(1) One thing I don't like is I can send 10 fleets to an AI's largest 10 planets. Then on the turn I declare war, I can pretty much capture those 10 planets generally locking a victory even against a stronger opponent. On the flip side, if an AI declares war on me, only then does it start invading my "space".

Suggestion:

Introduce the concept of air space (space space?). Allow a player to attack ships in their space without declaring war. This would put humans and AI on more fair terms when declaring war. Because if I started sending warship ships into the AI's space, they could move their fleets in and destroy them without declaring war.

Or a simple alternate suggestion...make it so you can't attack the first turn you declare war. This would give the AI a chance to attack any war fleets that were pre-positioned at their planets.

Note: obviously freighters should be given a free pass.

(2) There's been games where I have an Alliance with all the remaining races (diplomatic vicotry disabled) and I pick them off one by one.

I would like to see the AI break Alliances if our relationship falls too low (having an Alliance can be a + though).

I also think Alliances should work more like NATO. If I'm in an alliance with Race A, and I attack Race B, and A and B are good buddies, Race A should threaten to break our alliance if I don't declare peace on B.

Or moreover, being friends with a race's enemies should count against you (as well as being enemies with their friends). Too many times there are AI's that sit around in watch wars because they are friendly with both sides.