I think I understand the reasons why Multiplayer was not included in Gal Civ 2, and I agree that it would probably not be worth the time and effort. However, the main feature of Multiplayer I miss having is the ability to stage battles between 2 human players. I think it would be neat if a mode could be added where a person had access to all the technologies and could watch a battle between ships he/she created. I find the battles very fun to watch, but unfortunately most of the time I end up watching pretty small scale battles and think it would be fun to be able to watch huge battles take place.

I'm not certain how long it would take to add a feature like that to Gal Civ 2, but since the algorithms for the battle have already been made, and there is already a ship editor, it seems like it shouldn't be too hard.