The first thing I believe could be improved on battle system is adding the capability to follow the fight while it is happening, currently, the battle is to far from the user.
Secondly, the battle system should be more interactive. Maybe letting the user use some strategy like moving units back or toward the frontline for some advantage, putting units in defense/attack modes, dividing units into more regiments becoming able to divide an powerful attack force to more than one attack and also being able to divide enemy power advantage.
Let me know what you think about it.
Cheers,
CaioToOn!