While I hate to brag, this is relevant to this thread: I have more than 10 years experience in historical fencing. And I've fought with spear/axe/sword/mace against spear/axe/sword/mace in any combination. This is conversion of my experience in Civ/FFH terms.
It is important to understand that at least two other factors must be included in this discussion: shield and formation. Finally, I think it is good to add non-spear polearms, like halberds and lochaber axes.
Formation is definitely most important thing in melee warfare. This was best proven by Romans, but Macedonians were notable users of formation before them. In Ancient Rome there was well-known saying, describing the power of formation.
Lone barbarian always defeats lone legionnaire.
Ten barbarians versus ten legionnaires is a balanced fight.
Hundred legionnaires will destroy hundred barbarians.
Whole legion will defeat unlimited number of barbarians.
Of course, it is just a saying, and legions had their losses, but in general — that is correct.
Formation upgrade shouldn't just grant some power against mounted units. I think that it should be available only to "civilized" civilizations, so Doviello and Clan are excluded. Magic-based civilizations and pacifists like Elohim too are excluded. This noticeable flaw should be balanced by some other means.
Formation should grant unit a bonus against all units, like combat. But it can only work if unit is equipped with formation-friendly weapons. Formation grants great protection against barbarians, because they can't use it. Beelining formation-enabling technology really helps against these hordes of lizardmen and goblins.
This upgrade should come only from some special "Drill Barracks" (or something) building. When it is built, it overwrites usual barracks. Instead of providing units with +2 experience points, it provides them with the Formation upgrade for free, and does not provides them with additional experience points. It should be impossible to gain formation by normal means, for experience points. Maybe some magic spells could provide it, but definitely not raw fighting.
Now, on weapons.
Improvised weapon: default club. Or something other. In general it works like mace, but way weaker. This "promotion" just means absence of any other, more sophisticated weapons. Can't be upgraded by metal.
Sword: if we are speaking about medieval european one-handed swords, then first thing is first — swords are designed to be used with shields. Without shield, sword is still good weapon, because if we are thinking about at least type XII, with pronounced crossguard, then we do have great parrying weapon. But anyway, to evade extra complexity (and I doubt that this idea evades it at all, but still) we will suppose that it always goes with shield.
Two-handed sword: much more modern device. Great offensive weapon, but can't be used in formation — it requires large space to be wielded. Of course, it can't be used with shield.
Spear: first strike. Great in formation. Shorter spears can be used with shields. Very nice weapon, to be honest. Actually it is not that easy to hack down the pole with an axe. It is possible, but not easy.
Pike: Longer spears are actually becoming pikes and can't be used with shields. This is the best formation-friendly weapon.
Mace: similar to one-handed axe, actually — this weapon is armor-killer. One-handed bearded axes can be used for parrying and for shield destroying. I think it is good idea to merge mace and one-handed axe into one weapon for purposes of this discussion.
Two-handed axe: similar to two-handed sword, greater damage, lesser parrying ability. Much cheaper to produce than two-handed sword.
Polearm: similar to two-handed axe, but can be used in formation. Less damage.
By the way, different weapon types should come with technological advances. For example, two-handed sword is a _very_ late invention. Spear and mace are most early ones. Two-handed axe, polearm and pike are somewhere in the middle. And not every civilizations should have access to And I excluded more "exotic" weapons like scimitars and whatnot. They can be included as faction-specific promotions. Most of them are faction-specific anyway; I can't imagine Doviello in plate armor with two-handed swords.
Now, on possible weapon bonuses in game terms.
Formation: +50% against units without formation. If enemy unit has formation, nothing happens. All heroes and some magical beasts ignore formation.
Shield: protection against arrows; +20% strength.
Improvised weapon: nothing.
Sword and shield: shielded; +30% against improvised, mace, spear and pike; can use formation.
Two-handed sword: +50% against melee units; additional +50% against melee units on attack. Shock as it should be.
Spear and shield: shielded; +1 first strike; can use formation; +50% against mounted units on defense.
Pike: non-shielded; doubles formation bonus against units without formation; +25% against units with formation; +25% on defense; can't be used without formation; +50% against mounted units; additional +50% against mounted units on defense.
Mace and shield: shielded; ignores shields; lowers enemy armor on 1 level; can use formation.
Two-handed axe: +100% against melee units on attack only, ignores shields; lowers enemy armor on 1 level.
Polearm: +50% against melee units, can use formation.
By the way, if we are going this way, then we should have some armor promotions. These works just like combat promotions, but they aren't bought with experience. Notice that mace and two-handed axe lowers enemy armor on one level. Thus, if you are going against enemies covered in Lamellar or even Plate armor, consider to take some can-openers. Plate becomes Lamellar, and Lamellar becomes Mail. Even better (or worse): crossbows and arquebuses lowers enemy armor on one and two levels relatively.
Padded armor: 10% strength, requires any crop resource. Very low price.
Leather armor: 15% strength, requires any animal resource. Average price.
Mail armor: 20% strength, requires metal, weakness to lightning. Average price, not higher than leather armor.
Lamellar armor: 30% strength, requires metal, weakness to lightning. High price.
Plate armor: 50% strength, reqires metal, weakness to lightning, can be used only on units of 5 level or higher. Extremely high price.
And, at last, something about ranged weapons. If we are going this way, then ranged weapons too should work as promotions.
Sling: +1 first strike chance on melee units without shield; +50% against animals. Available at Hunting. Default weapon upgrade on ranged units.
Bow: +2 first strike chances on melee units without shield; +100% against animals.
Crossbow: +1 first strike on melee units without shield; +100% against animals; +20% against melee units; lowers enemy armor on 1 level.
Arquebus: +100 strength; +1 first strike chance; +200% against animals; ignores shields; lowers enemy armor on 2 levels.
Both weapon and armor promotions can be bought for a unit in city with special building. They don't require experience: only gold, relevant technologies, resources and buildings to produce them. Heroes, at least of melee variety, should be able to use them.
Thus, basical melee units could be something like this:
Warrior: 3 strength, 1 move, +25 city defense. Can use armor up to Mail. Can use any one-handed melee weapon. Can use crossbow.
Footman: 4 strength, 1 move, +10 city attack. Can use armor up to Lamellar. Can use any melee weapon. Can use ranged weapons up to crossbow.
Armsman: 5 strength, 1 move, +10 city attack. Can use any armor. Can use any melee weapon. Can use ranged weapons up to crossbow.
Champion: 6 strength, 1 move, +25 vs. Melee Units. Can use any armor. Can use any melee weapon. Can use ranged weapons up to crossbow.
Champions can be promoted to familiar heroic units: Berserker, Eidolon, Immortal, Knight, Paladin, Phalanx. They are mostly fine as they are. Of course, all of them can use all melee weapons. Ranged are probably prohibited completely — they are melee specialists. And for flavor, Berserker can't wear anything better than Leather armor, but it should be balanced with his relatively higher base strength.
Ranged units:
Scout: attributes as usual, except +50% vs. Animals, because it is provided by weapon. Can use armor up to Leather. Can use any one-handed weapon, but shield is out. Can use sling and bow.
Hunter: attributes as usual, except +50% vs. Animals, because it is provided by weapon. Can use armor up to Leather. Can use any one-handed weapon, but shield is out. Can use sling and bow.
Archer: 3/5 strength, 1 move; 1 first strike. +20% chance to do 10% damage to units attacking this unit's stack. +25% City Defense. +25% Hills Defense. Can use armor up to Leather. Can use ranged weapons up to crossbow.
Marksman: 5/7 strength, 1 move; 1 first strike. +30% to do 15% damage to units attacking this unit's stack. +25 City Defense. +25 Hills Defense. Can use armor up to Leather. Can use any ranged weapons.
Sniper: 8/10 strength, 1 move; 1 first strike. +40% to do +20% damage to units attacking this unit's stack. +25 City Defense. +25 Hills Defense. National Unit (4 Allowed). Can use armor up to Leather. Can use any ranged weapons.
As you can see, Snipers are fancy name for FFH default Crossbowmen. I find it somewhat strange that Crossbowmen are National Units, because crossbow is very available and easy-to-learn weapon. It was common sight, and it definitely wasn't some sort of "elite" weapon. I also somewhat nerfed Snipers raw power, because 9/13 plus arquebus 100% bonus would be ridiculous. It is probably ridiculous even now, though.
Two kinds of cheaper offensive specialists also could be trained. These are historical-friendly crossbowmen and arquebusiers. These guys aren't some kind of sissy city defenders. They go on offence with melee army.
Crossbowman: 4 strength, 1 move. +20% chance to do 10% damage to units attacking this unit's stack. Can use armor up to Mail. Always use crossbow.
Arquebusier: 5 strength, 1 move. +30% to do 15% damage to units attacking this unit's stack. Can use armor up to Mail. Always use arquebus.
To be honest, I don't really understand how is that walls don't offer any protection against primitive gunpowder weaponry. Tell that to all these people who continued to build heavily protected fortresses up to XX century. Probably game balance, though I'd used special city-sieging mortar squads. Oh, and right now I will add them as suggestion. If they are in game, then arquebus should lose its' wall breaking ability, and probably should be nerfed somewhat in raw power.
Mortar squad: 5 strength, 1 move. +100% City Attack. Can use armor up to Mail. +1 first strike chance; +200% against animals; ignores shields; lowers enemy armor on 2 levels; ignores city defense. Can obtain Barrage I promotion, but no more than that, and not initially.
Now I have to say something about flanking promotion for mounted units. Right now it allows you to escape if you are losing, which is somewhat cool. But real power of flanking should be... ignore of formation and defense bonuses. Pikemen aren't THAT lethal to heavy cavalry. Even in case of frontal charge, true gen'd'armes tend to overthrow pikemen. In case of flank attack, cavalry triumphs.
I propose to rename current "Flanking" promotion into something like "Recon Attack". And this is what I feel Flanking should be.
Flanking I: Ignores formation. Spear/pike bonus still applies.
Flanking II: Ignores formation and spear/pike bonuses, except additional defense of pikes. 1 First strike.
Flanking III: Ignores formation and spear/pike bonuses completely. Guaranteed first round win. 1 First strike.
And another nice mounted promotion line: "charge." We need something against these pesky archers.
Charge I: shielded; +20% against ranged; 20% chance to attack random ranged defender instead of the one best available.
Charge II: shielded; +40% against ranged, 40% chance to attack random ranged defender instead of the one best available.
Charge III: shielded; +60% against ranged, 60% chance to attack random ranged defender instead of the one best available.
Phew. It went longer than I initially thought it will be. I am not great in number-crunching and balancing, but I think these numbers are somewhat realistical. If something here breaks balance badly, it should be toned down, of course.
Hope someone more productive than me will be able to use this feedback to create something good.
And to be honest, I couldn't care less about graphics. I mean that it isn't necessary to model each and any combination of race-specific unit, weapons and armor. Half-naked standard axemen model works fine with me as plate-armored footmen with pikes, if promotions are easy to spot on mouseover. Though of course, if it is possible to model all of that crazy goodness — that's just perfect. If it goes in game, of course, what I am in doubt of.
