I like the idea of tactical battles, but I think there's a lot of untapped potential there.  There are 2 things I'd like to see:

1.  I really wish I could move units through spaces that are occupied by allied units.  Basically the rule would be that you can move through a space occupied by an allied unit, but you can not end your movement in a square occupied by an allied unit.  This is similar to the way tactical movement works in pen and paper RPGs like D&D.  It's rather irritating to have to waste unit actions to move them out of the way when there's no good reason for an allied square to block your own movement.

2.  I'd like to be able to choose where a unit starts in a tactical battle.  This is obviously a more complicated idea than my first suggestion, so let me explain further.

I envision this as a sort of short pre-battle planning phase.  The player would be presented with a cloth map equivalent of the battle field, showing obstacles, terrain modifiers, and enemy unit placement.  The players would be able to drag units from their stack and place them on their side of the battlefield in any square the unit can occupy.  Then once both players have clicked the ready button, the battle starts.  This does 2 things that I think would be beneficial to the game.  It gives players the ability to protect certain units in the stack by making sure they are as far from the battle as possible.  It also prevents annoying things like having the game automatically place your good melee units in the back of the line while putting spell casters at the front.  On top of that, it can be used as a loading screen for the 3D battle map, thus eliminating the ugly clouded view of the map you currently get while it's loading.