Well, I mentioned Colonial because it's an "official" variant, it's a real board game variant/sister of regular Diplomacy.
The only "fan" variant I've ever cared to see in action, as a fan of Italy, is "Fleet Rome," where, true to the name, Italy starts with a fleet in Rome, rather than an Army (which would really make Italy more resepcted in many palyer's eyes, I think, since really, if Italy becomes a pwoer on the board, it's due to her fleets, after England she's arguably the nationj most depent on them, so that swtich just makes sense.)