i agree, i mean, if you had to micro manage the ground battle that wouldnt be good. i cant see throwing in a whole new interface and controls etc to control tanks etc being worthwhile.
however i like the idea, perhaps you have the option to bombard from orbit, but then have to rebuild everything, or, send in troops and get a bonus (i.e. you get cheaper labor, higher taxes, new tech) to balance it it could be that bombing is guaranteed, while sending in troops has a 50% chance of failing, but you get the bonuses, also you have the option to continue sending troops and resources etc until you have to make the choice to continue your exceptionally expensive ground campaign, decide to simply bombard from orbit, or retreat. with each having consequences (i.e. the more troops that die and the more you have to send reduces combat effeciency etc)
also, i think that planet should be able to defend itself. i mean, what, we have empires spanning solar systems and galaxies and we somehow forgot what a surface to space missile is?
however, i have to say though, quite simply, that if you had to micromanage the battles on the ground, that would suck, its a Space based RTS game, having a whole game inside a game may be cool if they pull it off, but i doubt it will work. not the way sins is now.
good idea though