It could be cool to have reinforcement feature as "normal" player (not AI) in battle generator. Now you must think carefully what units to choose before battle. I must confess that I choose too much tanks often

(maybe I hate losing battle to AI

)... So winning is too easy that way. That's why it could be nice to "share" some tank units into another later phase of battle (let's say turn 12 AI will add 5 tanks and so on)...