I prefer single phased games in most respects, but feel that the game engine could do with some improvements to strengthen the defender.
The most important consideration is whether the current system is biased towards the attacker. Unfortunately, the ADF system seems less reliable for the ACW engine than for the Nappy one - it's quite likely that defending units won't fire at all, let alone three times, so firing at 50% strength means that the attacker has an inbuilt advantage. So, I'd recommend increasing the probability of defensive fire or putting this into the pdt file so that players can determine this themselves.
Also, there seem to be too many melees occurring, which seems unrealistic and again favours the attacker. So, maybe attacking units should only be able to melee if they've only used up 1/3 or less of their movement allowance?
The action point system of the WW2 engine makes it much harder for units that have moved to melee - maybe this would be a useful system for the earlier games too, since movement, firing and melee are linked, whereas in the current engine (for the ACW, EAW & Nappy games) a unit can use its full movement allowance, fire at full effect at point blank range and then melee as well! With an action point system, a unit that's moved gets less firepower and if it has used its full movement allowance it can't fire at all, let alone melee. However, the (stationary) defenders will be able to fire up to three times. So an action point system would actually discourage rather than encourage blitzkrieg tactics.