Don't want the players going on Genocide runs? Funny, I thought that's what Invasions Tactics already were... *rolls eyes* Heck, what about the poor players of that new sect of Drengin in DA? I thought they were ALL about Genocide Runs?
But seriously... I would like to see Orbital Bombardment. Here is my little "proposal":
Orbital Bombardment weapons would be completely different modules from Space Combat weapons. Although there would be Beam, Mass Driver, and Missle Bombardment weapons, there would not be any real difference between them (or they could be a seperate Tech from the other weapons, much like Starbase Fortification... but... I'd rather not, simply because I think the Starbase Fortification Tree is stupid as it is currently).
You could not Bombard a planet that has defending ships (at least without some other Technology... say.. CLOAKING

).
Bombardment would simply be a reduction in Population, Morale, Influence, and Industry/Research Production each turn it remained under siege. Planets reduced to low morale might surrender to the bombarding player (a chance based on the morale left). Improvements and Planet Quality aren't damaged/affected.
The amount of "damage" done to each of these stats would be a percentage between 1% and the Bombardment Quality of the weapons being used, with each stat (pop, morale, etc) being determined seperately. Planetary Defense would reduce this damage in some way.
Population Growth would be halted each turn a planet remains under siege, or at least reduced greatly.
Damage done to Morale, Influence, and Industry/Research Production would repair itself over a number of turns equal to about twice the number of turns a planet was under bombardment. The Civ may pay money upfront to make the repairs go faster and planets with higher Industry Production would repair faster.
A couple of rough edges, but I think it works within how Invasion Tactics are already handled...
Now... as for Carriers... I really don't care too much about them, but I would say that some form of Mobile Military Starbase
called a "Carrier" could work. Their Range would subsitute the range of smaller ships up to a certain Logistics amount.
Plus, they could provide other benefits to ships in their fleet (even larger ones) like increased Repair value, increased Defense, or decreasing the Defense of enemies they attack (hmm... wonder where I got those ideas?)
So... it could be a "Basic Carrier" module that extends its life support up to 6 logistics points of ships up to sizes smaller than it. Thus, a medium ship with one of thse modules could support up to 3 Tiny ships. A large could support up to 3 tiny ships or 2 small. A huge, 3 tiny, 2 small, OR 1 medium and a small (I think). You could add more modules to support more ships, 6 logisitics points each, but you still could not support more ships than you could put in a fleet normally.
The Basic Carrier Tech would be off the Medium Ship building tech or Advanced Logistics or so. Advances would let modules support more Logistics each, as well as seperate ship modules that provide small benefits to all supported ships (ie: the attack, defense, and repair bonuses).
After further thought, maybe it would be better if the Modules just supported all ships of the correct sizes in a fleet, but would be more expensive and larger in size... *shrugs
Well, those are my ideas. Simple and effective, I believe. But, it's whether or not the AI can use them effectively. Sadly, as great as the AI is, it could also be the game's greatest weakness... keeping up the "good AI" appeal means limiting options it (and henceforth, the player) can do, sadly.