Ok, Ahriman, I can see where you´re coming from. You like games to be elegant and simple, like chess, which is the king of strategy games and reserved for those with high brain volumes.
Here´s my proposition which takes your consideration into account and keeps the amount of different values to a minimum.
My desire is to reflect history as realistically and faithfully as possible.
Combat in my view can be divided into eras, there is the MELEE ERA, that is from earliest ancient warfare to about 1500´s or 1600´s, when muskets started appearing en masse, early muskets were clumsy and slow to fire and needed to be escorted by spearmen, that is melee units, that is where the famous Spanish Tercio formation comes from, musketmen escorted and protected by spearmen (there´s another Spanish unique unit, a musketman with a +50% bonus against cavalry due to the spearmen, the Tercio). The Tercio ruled warfare in Europe at the height of the Spanish empireand was replaced as a tactic by advances in weapons technology.
After the development better muskets and the bayonet, which made a musket into a part-time spear, the musketmen were able to protect themselves against cavalry and came to their own, from this the age of the firearm begins and muskets were the basic from 1600´s up until after the US Civil War in 1860´s after which warfare was revolutionized by breech loading rifles and increasing firepower.
In the age of the musket the standard tactic was to march large numbers of men in close formations to increase firepower, you simply made a man into a marching musket, all he needed to know was how to fire and load a musket and how to stay in line. This is the time of linear tactics, lines of musketmen firing at each other at close range followed by a melee assault with bayonets.
Paradox Interactive, makers of map-based strategy games based on history, use MORALE as the basic combat value for their games of the ancient Roman times and for Europa Universalis series which is set in 1419-1820, the era of the musket.
Units have morale and do SHOCK DAMAGE (a melee charge or a cavalry charge causes shock damage, SHOCK is a promotion in Civ 4) to each other shaking each others morale until the loser withdraws, armies are seldom destroyed, they take casualties and battles are lost, but they are seldom completely destroyed.
What decides wars in Europa universalis is MANPOWER, each nation produces manpower according to it´s population, manpower means how many soldiers there are available for recruitment at any time, your nations manpower pool, a small nation cannot support an army of millions like realistically, armies need a continuous flow of manpower to resupply their ranks for casualties and retirements, hence you must have a large population to support a large army, in a small population there simply isn´t enough fit men to supply the ranks and you cannot conscript every last one, you need men to work the farms etc.
I propose adding MANPOWER to Civilization, every population point produces manpower points and units require manpower to resupply and heal, hence you can lose a war by having your nation bled dry, your units cannot heal because you´ve run out of manpower.
In addition MORALE would be added to the combat system as a new value. This is because morale shifts over time and is affected by several things in a civilization.
In combat the computer throws TWO sets of dice every combat turn, one dice for melee or firearm damage to hitpoints and a second dice for MORALE DAMAGE or SHOCK. If morale runs out the unit withdraws, so you can win a battle in two ways, by destroying the unit physically by reducing its hitpoints to zero or by forcing it to withdraw by reducing its morale to zero.
This would reflect history very accurately and would keep the amount of values to a minimum of TWO. MORALE and STRENGTH
ORGANIZATION can be merged with MORALE and STRENGTH, poor organization reflects in lower attack and defence strength.
DISCIPLINE is a modifier to MORALE or can be merged with it, for example discipline affects how fast unit loses morale in combat or so.
LOYALTY affects on a strategic level and can be simulated by units turning barbarian if they are not paid.
MORALE can also be simulated using just one value, by using withdrawal as a tool, all units begin with a high withdrawal chance, they have poor morale and will break easily, promotions REDUCE the withdrawal chance, making the unit hold its ground better.
I would also add COMBAT EVENTS to Civilization, random events that affect combat, in combat there is a chance every combat turn that a combat event occurs, reflecting a changing battlefield, tactics, random elements, etc., for example, combat begins and suddenly there is a combat event "tenacious defence", the defender gets a +100% bonus decimating the attacker. Combat events are used in Paradox´s games and the old Panzer General series which has inspired makers of Civ 5, for example the hex grid is inspired by Panzer General.
So basically, you CAN simulate morale with just one value, just use the withdrawal in a different way.
MANPOWER would place a cap to how much units can heal, you cannot heal if you don´t have manpower points available, that would solve the problem of all units just withdrawing and not getting killed, eventually they begin to die because the opponent has run out of manpower and cannot resupply his/her army.
There´s my proposal.
Cheers!
PS. I would keep stacking, Panzer General had one unit per tile and it had problems with roads getting clogged and units not reaching frontlines, hopefully it is possible to mod stacking back into the game later on since they have decided to drop it.
Also, I would make the combat system fully moddable so everyone can create their own system.