In order to "improve" uniques, I would scrap them completely. Imagine having YOUR country in the game, AND the ANCESTOR of your country, and any country you may want to play... This would be all be possible if we scrap uniques, except for names and city names of course. This way, the work of the developpers would be focused on integrating EVERY CIV IN THE WORLD PAST AND PRESENT instead of mere uniques you barely pay attention at past the effect of discovery, if there's any.
This, associated with the option to be able to start NEAR culturally linked civs would make for an AMAZING roleplaying, like recreating History, really. For example I'm French, I would totally love to play the Franks, surrounded by the Goths, the Vandals, Rome, why not even Carthage, etc... or playing regular France with England (I hate England with a passion), Italy, Germany, Spain, Dutchland, Belgium, Switzerland, Luxembourg (city-state ?), etc. etc. all around.
Not to be mentionned we could play on Earth map, with every civilization covering the land... but of course not in actual-like Civilization, because the turns would take forever. Maybe in an upcoming game that finds a way to fullfill empty areas with non-computer-consuming-power stuff. (like "City-States" -barbs, minor civs, whatever you want to call them-, but working *VERY* differently than actual civs, like having abstract units and all, and dealing with them would be like sending spies to them) EXAMPLE : what about having a whole areas depicted in RED, without cities but marked as populated with barbarians, in which no single civilian unit could survive more than 1 turn, and military units being constantly harrassed by barbs units spawns...
Wow, that got far.