Piranha,
I understand what you want to do.
But unless players manually control the units or get a fair bit of control over the units how will you guarantee a Wizard/Elf gets to face a flier? You'd have to write logic into every unit since an AI would be controlling them. So in addition to Wizard/Elf trying to get to a flier you'd need logic for a flier to avoid/run from such units and only attack ground units as it's a pointless system if the flier doesn't try to avoid such units. That seems awfully complex on your side. Same with units avoiding piercing damage etc.
Plus right now fights are always 1-1. But if you had 3 units and your opponent only 2, you should get a 2-1 battle someplace. How would that be handled? Or a fast moving unit that moved 3 could literally always run from a slow moving unit that only moves 1 such that it could in theory perpetually avoid combat.
You'd need an awful lot of simulations to figure out how to handle that and deal with 2-1 attacks and AI's for all kinds of different units. Otherwise you get something that's not really any different than what you have now.
The strength of the current system is that it's got tens of thousands of games (War2/DLR/Warbarons etc) played on it to help balance things. A new system would need a tremendous amount of balancing effort. This would have to be done by computer simulation since games take so long to play that you'd end up taking a year just to get this kind of combat system remotely workable before you got down to the final balancing.
KGB