If you go back to the original ad material for MOO3, it was much more a grand strategy game than it turned out. The developers discussed how deciding to have a floating or fixed currency would be a major decision. If you were floating, but the Antarans took a dislike to you, well... they dump on your currency, and POOF! goes your economy.
Personally, I'm rather glad it didn't end up that way. MOO3 still ran way too slow to be much fun, in my opinion, but it did have a lot of good ideas.
I love the Master of Orion series, and a MOO3 remake might be interesting. I agree with Khan, though - a small scale update of MOO1 or MOO 2? Meh.