Retreat mechanics is the main thing which is broken in my opinion, if you could fix this mechanic during development this would improve the game immensely.
The issue is that your company is virtually immortal if you retreat as soon as things are against you, because you just get a temporary injury which heals on all members. It is also asymmetric because the AI opponent cannot pull this move but you can, hence it is a massive cheat.
A) Randomly allocate minor injuries, permanent injuries, and deaths (according to some improved and more realistic formula). This is the most basic and least desirable, but better than the current system.
B) Auto-calculate the actual retreat at high speed, in other words the AI takes over and tries to manually retreat the men step-by-step, and whoever cannot reach the edge is killed. It just simply automates (rapidly) the actual retreat with AI control, and the consequences are final.
C) You could make manually retreating the company easier and actually viable instead of almost certain death for most members. The way to do this might be to hit a button (perhaps with a horn icon), sounding the retreat! (A nice horn sound could play. Note it should be a horn of retreat not a white flag of surrender – but I’m being autistic). Anyhow at this point the men could all have a retreat status in which they are unable to attack, but they are able to move through zones-of-control without being attacked. Also, perhaps their movement rate could be increased, or some other changes induced by the retreat. Perhaps they also have to drop their weapons and shield or something like (or a chance to do so), in order to be able to retreat at higher speed.
The retreat mechanics should be symmetrical for the company and the enemy. Whatever options for retreat are available should be available to both sides – hence making it balanced, realistic and not feeling like a cheat which breaks the immersion.
Fix the retreat mechanics and the game mechanics go from good to great – that’s my opinion.