I like to approach the whole combat simulation from the perspective of HOW WOULD IT PLAY OUT IN REAL WORLD, HISTORICALLY. (without too much math involved)
For example: An archer has a first strike capability representing the units capability to shoot at a distance, good that´s one way to simulate it, if someone comes up with a better system I´ll consider it, but first strikes work as a way to simulate ranged fire.
Here´s one problem though: The archer is strong as long as the enemy is at range and the archer can shoot arrows at them, but when/if the enemy manages to close the distance to melee range, then I´d expect the archers to be very weak, so in Civ 4 terms, archers have a +50% (or whatever you like) bonus IN THEIR FIRST STRIKES, BUT when the combat gets to melee, the archer has a -50% minus, because the archers are really not trained or meant for close combat, they might have daggers and knives as personal weapons, but that´s really weak if your up against a swordsman with a shield (a TRAINED swordsman, trained for melee combat, archers train for years to be good with a bow, NOT to fight a melee)
In the current system the bonuses apply ALL THE TIME, an archer with a +50% bonus against melee units is a real killer also in melee combat, when the bonus might be meant to ONLY mean a bonus in ranged fire.
So I think there should be COMBAT PHASES or COMBAT TYPES or SOMETHING to differentiate different combat types, you have RANGED COMBAT (archers, musketeers, riflemen etc.) and you have CLOSE COMBAT (swordsmen, archers if they´re attacked in melee, musketeers in bayonet charge etc.)
Ranged units might have a RANGE parameter in their data to indicate who fires first and who gets the upper hand in ranged combat, archers might have 300m and riflemen 500m etc.
Anyway, to the question, should there be 1 or more values in combat, I´ll say that the STRENGTH master value goes a long way, BUT I think that if you intend to simulate reality FAITHFULLY and represent ALL the different aspects that affect combat, you might need more than one value and IF you need more than one then use more than one by all means. As long as reality is simulated well in the model, I´m happy.
Cheers!
PS.
I´m one of those too who think that stacking is NECESSARY.
Reason 1: How are you going to fit large armies into islands like Great Britain or Japan? You CAN´T with a 1upt system, that´s ONE reason to keep stacking in my opinion.
Reason 2: How are you going to move multiple units at a time? I don´t know if Civ 5 will have ANY sort of a system to allow multiple unit movement and even with fewer units it´s going to make turns take longer and that´s BAD, besides I like LARGE armies, lots of resources for everyone so ALL can build MASSIVE armies and duke it out. Without multiple unit movement it´s going to take forever to complete just one turn. There´s another reason to keep stacking, multiple unit movement.
However, I know that stacking has a major problem aswell, it´s called the Stack of Death and that´s BAD. So I propose a solution:
It´s called STACKING PENALTY. All units in a stack incur a sizable (decide yourself what is sizable) -50% or more PENALTY to their combat strength, making combat in stacks impossible and making the so called Stack of Death VULNERABLE. Stacks would remain as "marching formations", but you would need to deploy from stacks to an open formation to do battles in the field like in 1upt. So basically you would have the best of BOTH worlds, you would have stacking to enable large armies in small places, to remove overcrowding on roads and to enable multiple unit movement AND you would have those cool field battles that they envision at Firaxis, inspired by Panzer General, which had a 1upt system and its problems of overcrowding on roads etc.
I hope there will be a MOD that enables all this, since they´ve already made their decision at Firaxis, so the 1upt side will have their needs met by the vanilla game and the "stackers" will need to mod the game.
Also I´ve heard that they´ve REMOVED religions??!! They must be insane at Firaxis to do something so unrealistic. That too needs to be corrected by modding. Let´s wait and see what else needs to be done for the game to be playable.
Any volunteer coders for a MOD project?
Cheers!