In the most recent episode of 3 Moves Ahead, commentators Bruce Geryk, Rob Zackny, and Troy Goodfellow talk about ancient warfare and in particular the many and disparate models of leadership in strategy gaming vis a vis the effect of leadership on combat in the ancient times. It is an interesting discussion and fits into a larger discussion of the general lack of ancient wargames.
I am far from a strategy connoisseur, but one of their comments made an interesting model jump to mind in my head. One of the panelists mentioned a theory that leadership in ancient times had their greatest influence on a battle before the battle starts, and in fact once it does they have relatively little control over the battlefield. This makes perfect sense to me, in no small part because it lines up with a few pieces of fantasy and fiction that I've read, and in particular it makes one wonder if perhaps that is exactly how it should be modeled.
Suppose for example that as part of a larger grand strategy game, two armies collide on a given macro-scale map. Each sector of the macro map represents either a smaller micromap, or a intermediate engagement map, and once the engagement begins, the skills of the two respective army leaders are compared and one is given the tactical advantage of choosing where on the map their units spawn, given only that the enemy is approaching from a given direction. Once they have chosen, the other general positions his forces a given minimum distance away.
There are options for balancing this strong tactical advantage back in favor of the second general, mostly to do with scouting the position of enemy troops before moving their own into position. A particularly poor general (or a particularly one-sided map) may prevent even that advantage, making the second general place troops without knowing the situation they are advancing into.
Obviously the bulk of this idea is that the better general on any given battlefield is given the distinct advantage of choosing where and how the fight takes place. Whether that means deploying their troops ready to charge, laying an ambush, or making a strong defensive fortification before the enemy can arrive, the general can make choices before the battle begins that end up being as significant if not more significant than weapon-type advantages.
I would combine this with another thought--that of squad leaders and other lesser command units that are responsible for having a smaller combat unit perform according to orders. As the commentators went on to say, the idea of perfect or even semi-perfect information in an ancient battlefield is, generously speaking, optimistic, and command and control is largely about making plans beforehand and only signalling basic concepts in semaphore or with loud brass instruments, generally conveying orders not much more specific than "advance" and "retreat".
Therefore, I would suggest that squad leaders would generally have their own dispositions--some charge recklessly, some prefer to turtle, and others perform exactly as ordered even when that is a poor choice. Likely, they would also be better at some tactics and worse at others, so ordering a turtling squad leader to siege the walls may lead him to make serious errors and waste his entire squad.
This leads to more choices made ahead of time--what sort of squad leaders to field in which positions--and in fact it is a sort of hidden information that on a grand strategic scale can be ferreted out about a given opposing army. Do you know that under General Whosit are six cavalry captains, four of whom charge recklessly, one who obeys orders strictly, and one who prefers to hang back? On a first order approximation you can expect, upon seeing Whosit's cavalry, that two-to-one their cavalry will charge recklessly--if you can set up an engagement you can perhaps trap the area in front of your infantry or ambush them with archers. If you are unlucky enough that they get to set the engagement, knowing that their cavalry prefers to charge, you might be able to goad them out of defensive emplacements--or perhaps you can expect that they won't turtle at all, and you can set up a defensive line instead of looking for them.
I imagine that leadership in the ancient era is about personalities--national, per army, and per military unit. If you know the character of the nation, you can guess how the army will be; if you know the army, you can guess how the units will be; if you know the units, you can tailor plans specifically to them. If these qualities of the units are real and tactically significant, then the question of ancient strategy comes down to knowing your enemy, and then using what you know against them.
I think it would be a fascinating sort of game to play, if done right.