Bump, because I really want to know the answer to this one as well.
Having UGC diplomatic missions would really help to reduce the current grind for diplomatic xp. More importantly, some of the best storytelling will involve some non-combat objectives and background material.
On the other hand, having UGC diplomatic missions would reduce the current grind for diplomatic xp. If you get my drift. I'd hate to see a way for diplomatic xp to get farmed with a bunch of gamed fast-click diplomatic missions.