The fact is, flat map would require something different than just brainless charge. Something different than running in circles inside little alleys. Something different than one team camping far best place on the map and the other team trying to conquer this place round by round.
I think its good reason to try this idea. Random plain maps always has some little terrain advantages in some places, which is the reason why teams camp there and dont want to move even a bit forward for few minutes. Flat maps without giving advantages in any place to any team will require organization, and wont prevent teams from moving forward step by step.
As addition to this idea, I think it would be great to have big, deployable, 3 slots, very heavy and hard to destroy shields in game, similar height, but wider than Heavy Board Shield (shielder can put this shield on the ground and later take it again), crouching (so shielders in front can hide their heads and let archers behind do their job), walking by pressing some button to activate it (every infantry would have same speed while walking, so they can move shieldwalls in organized way) and couchable pikes held by crouched pikemans (couched pike wont let pikeman to move, but every horse hitting couched pike will stop and receive damage).
This way shield walls could look really amazing: crouched shielders in shield walls, behind them archers and crossbowmans, and between them couched pikes (and other infantry) to prevent shieldwalls being smashed by horses.
Still, I think its just a dream. Infantry dont want tactics in this game. They just prefer brainless charge, and no cooperation at all, cooperation is boring in their minds. So it would be cool to see this in game, but Im afraid it's impossible to coordinate by majority of cRPG players anyway.