1: Show the benefits of tech treaties in the kingdom report, like it shows the gildar from economic treaties. Next, maybe even show a breakdown of the benefits by country.
2: Have "next city" & "previous city" buttons in the city build screens and city info screen.
3: Maybe increase the minimum distance between cities by 1. The map get awfully crowded, and some cities can't seem to build anything because they are too hemmed-in.
4: Add a "buy & equip" button to the item shop. Have it greyed-out if the character already has the item, or if they can't equip it at all. There have been similar requests in the past, and it's always been a pain checking what someone has before buying something for him, but it seems even more important to me recently since I keep seeing characters who can't wear certain boots, armor, etc.
Now some possibly not-so-easy ones...
5: Do something about the proliferation of unit types I will never build every time I research a new military tech. That was one of my least favorite parts of GalCiv 2, I saw it coming from discussions in the forums many months ago, and it bugs me as much as I was afraid it would.
6: Add a few more buildings that provide a fixed amount of gildar or research or whatever, so landing near the right resources isn't quite so critical. Now we have level-1 buildings that give us 1 of something, and later buildings that benefit about 25%. Sorry, but an extra 25% of 1 isn't very impressive. Or maybe even some higher-level spells to give more benefit than the early spells that give 1 food/material/research. Maybe also a spell to give gildar.