Personally i like combat, but it's less interesting than other aspects. I prefer a few interesting battles to constant strife.
...Regardless of how important and detailed combat eventually becomes, I think the one vital option would be an auto-resolution option in both single and multiplayer.
In single player, it allows players who value combat to fight them through, while it would allow players who prefer the strategy of the main map the option to forego what to them would be needless combat. In multiplayer, if one player selected auto-resolve, we could prompt the other to see if they wished to use it as well. IF they did, both sides could use AI to be resolved. IF the 2nd player chose not to use auto-resolve, the 1st player could be notified and be allowed to reconsider their decision.
I strongly agree, though i'd implement it a bit differently.
The trick to balancing combat with the rest of the game for multiplayer seems rather tricky. I haven't played Moo multi-player, but it seems that the pace would be agonizingly irregular. There isn't something to do every turn. If the turn where you wanted to immediately press "end turn" after glancing at your sit-rep happened to coincide with a large battle fought by other players, and battles were long, how would you ever finish a game?
Moo2 vs. Moo1 seemed to contrive things with command points so that your fleets and ships were much fewer. That felt rather artificial to me, but it seems that something like that would be necessary to make MP games playable without totally skipping combat.
I believe a max turn limit for combat will be of some help here. Assuming 5 sec turns, a 100 turn combat would take 8.3 minutes. This seems too long to me. Perhaps 50 turns max is a better default, (though this could probably be a server option). Combat that exceeded the turn limit would be continued the next turn.