Well not all of these are likely up-to-date for version 1.4 but I think you should check out:
Naselus' Insane Abundance Mod, which rebalances things for larger maps, and generally works on making the AI competitive. This is definitely not up to date with 1.4 at this time of posting.
Grallonsphere's Stellar Diversity mod is awesome, and much of its features should become standard in future versions of GC3
Deathwynd has multiple mods that are quite good. They increase the variety of anomolies, planet traits, and even racial traits.
and of course, my mod will give you a huge assortment of custom shipsets and appearances that the AI WILL use.
I believe all of these mods are compatible with each other. But some may not yet be working for 1.4 of the game.