How about some new techs that can affect ground invasion. One of the options for ground assaults are mass drivers. Why not have an orbital bombing invasion tactic that is based on the current technology in bombing. You'd start with small bombs that do little damage to people or structures. You get more and more destructive until you got to the "nuclear" type bombings which modified PQ as well as were quite massive in damage to structure and population. Then you'd also have precision bombing with smart bombs that attacked specific structures(orbital fleet manager). This bomber would be part of a regular fleet, not the assault fleet. Sometimes you destroy all the fleets in orbit just to wait a number of turns to have your assault ship arrive only to find more ships in orbit again. Would be nice to take out that OFM the first time we visited. Maybe just bomb the production or research squares. Certain tiles would be offlimits. And the smart bombs could target mainly the military infrastructure, so it would reduce those part of the population that would take place in the ground offensive(ie lowering the number of soldiers).

Brian