[Comar]

I still play Emperor of the Fading Suns on a regular basis in PBEM, but the tactical aspects of ground combat are not that great in it either. The two stacks just go at it without any imput until a decision is reached, much like this model. The difference is that the entire planet is not conquered in one turn, like here. It can take quite a while to conquer a planet, particuarily when playing against a human opponet.

The suggestion of using the existing model of warfare is a good one. It isn't perfect, but it could work. The only problem would be that it would only be for single player, not multi.