The 500 day reward ought to be one of several small things....
a] One opposing faction costume piece [Klingon sashes would look pretty bad-ass on a Terran Empire costurmes...]
b] Opposing faction pet [btw, where are the dogs /cats for the humans in StarFleet?]
c] A trophy for your ship's lounge /Captain's Office
d] A purple level tribble usable by all races /factions
e] Ok, this is my favorite, so I'm biased... EARLY ACCESS TO ROMULAN FACTION CONTENT! [I can dream, can't I? ]
All the other 'been-there-done-that' rewards have had comparatively small in-game effects, and I think this should too.