I prefer the idea of this being a game mechanic. To me, this is something that makes the UP more than just a "every so often, all us races get together and we vote on stuff.." As I've already stated when it comes to Espionage, the UP and it's inner workings or inner not-workings would add an extra layer to GalCivIII to those like me who prefer espionage/propaganda/etc to violence as a first option.
Essentially, I think the UP should be more like the UN: Maybe not so far as to have a Security Council where all permanent Members have Veto Powers (real life complaint), but where it's not just a case of "I vote to punish the Drengin, they have to do what the UP says!" The Drengin can make a case against the influence the Alterians have on the UP and how their automatic bias against the Drengin means the UP is basically an Alterian War Court etc...
This, of course, lends itself to the idea of several races breaking away from the UP and forming their own council. Not sure if Stardock see that as a worthwhile idea to work on and to be fair, what do you do if the UP spawns a Mini-UP which spawns a More-Mini-UP??