Well, I'm playing as the Drath (who, in their story, are good at manipulating politics to play other races against each other). I have maxed diplomacy (in fact, I have the highest Diplomacy possible without cheating or getting lots of special anomalies). I have a much higher espionage than any other race normally does, including some anomaly bonuses, and I have "Advanced" espionage on all other races. I have a Galactic Bazaar. Now, I'm trying to pay the evil Korx (galactic mercenaries, who even attacked the Altarians on behalf of the Drath in the story, remember?) to attack the good Torians. Now, the Korx have WAY more of EVERYTHING than the Torians, they're sharing borders, they're even "Hostile" to them. I, on the other hand, am on good terms with the Korx ("Warm"), though I'm not allied to them. The Torians are bothering me, I don't have any ships, and I want them gone--but can I hire the Korx to squish them? HELL no. I offered 40,000 bc, 200,000 ip, several high technologies (VR Centers, Xeno Farming III, Starbase Fortification, Ultra Life Support, Industrial Sectors--y'know, nothing that'll actually help the Korx against me), and the morale trade goods. So much for "Our incredible diplomacy advantage." Just out of curiousity, I added things until they accepted--it took 5 planets, 4 resource starbases, and 2 military starbases to get my offer to turn green. I (obviously) cancelled out of that. Further tests on other races would suggest this to be normal, too.
So, I'd like the ability to be able to get other races to go to war WITHOUT donating my own empire to them for it.
I'd also like more active minor races (such as I actually had once when the Scottlingas glitched and started invading people, most of them successfully).
I'd also like the ability to change my close-in view of the galaxy to the simplified symbols you see when you zoom way out. Not permanently, as a mod, but just a simple Ctrl-Something hotkey to toggle a simplified display.
Edit: I'd also like the ability to see the researched techs by category in my espionage reports. It's annoying having to sift through huge lists to see what types of weapons and armor my enemies use, I should at least have a smaller and more focused list.