As for the question of romance and defining 'gen', I'm inclined to follow the show's lead. So some flirting, some banter, a lunch for two - but only incidental to the main plot. Enough to flesh out the characters, perhaps, but no more.

Yeah, that's my definition of gen, as well -- the level of romance, and the romantic relationships, seen in the show. So, Rodney getting interrupted in the middle of lunch with Katie to go save the city, or Elizabeth reflecting on Simon while being held hostage by Genii, is perfectly gen in my head. Rodney spending all his waking hours obsessing on Katie, or Sheppard kissing Elizabeth (while not possessed, that is, *g*), or a story that's *entirely* about Rodney and Katie's date is not gen.