Also, wasn't the galaxy map in MoO3 in 3D as well? Of course, you could only travel from star to star, but still. I found it pretty easy to use.
I Moo3 you ordered ships to move from star A to star B. Nothing ever happened in the middle as far as I remember as you couldn't intercept fleets, only fight at the star system that was their destination. Even if you didn't use the star lanes to move and cut across deep space there was no interception. So the 3D map was eye candy with no real strategic importance.
In gal civ you can can intercept enemy fleets anywhere, in orbit of a planet or not. This means that the AI needs to think in 3D and calculate which location to move into for best effect. Currently the AI calculates it's route to target and moves along the shortest distance, if it encounters a threat in the squares ahead it may recalculate and retreat. Add in 3D and it has to calculate alot more variables as there may be hostile units in front, above, below, to left and up, to the left and down....
There comes a point where the AI has to stop making calculations and act. With all this extra info to take into account we'll either see a big leap is processing demands and a slower game or a dumber AI failing to respond intelligently. The player will have an even greater advantage as we have a greater spatial understanding than the AI ever will.
But what are we gaining? Ok, it looks good. Does it add extra strategy? Does it matter if you attack a planet from above or below? Or the direction you approach a fleet from? Surely they can turn around when they see you coming across space? The UI will need a total redesign and careful implementation as you're going to miss-click one helluva lot more trying to select an empty volume in 3d space to move to.
It may work in Homeworld, but Homeworld is real time and plays nothing like gal civ, you get to twak movement as your ships are en-route, in gal civ you can move a long way off course in the space of a turn with no chance to correct. I'd rather see another graphics upgrade for the development time/cost of working out all these issues. The game would look better and you don't have to redesign the core gameplay to accommodate for a visual nicety. Gameplay and usability over visual gimmicks!