1) Civilizations that have left the UP should not be allowed to trade, I include here trade by freighters and diplomacy, with those that are still members. I know that when a civ vetoes a vote they leave and cancel all treaties with those still in the UP, but it is very easy to reinstate the treaties. Or at the very least you should incur some diplomatic penalty with members for trading with a non-UP civ.
2) All resolutions should be visible, with the exception of those unlocked by tech, not what we have now where you get 5 resolutions at random to pick from.
3) A way for a civ that has left the UP to return to it. Maybe when they ask to return a new resolution can appear and be put to vote.
4) A resolution for all UP civs to declare war on a member that has left.
5) The Diversity In Trade Act gives a bonus to a civ that has trade routes with all members of the UP, this is a problem in games with lots of civilizations where there are more civs than trade routes available to a civ. In one game I was trading with all major civs yet I still din't get the bonus, does it also require to trade with minors?