As cliche as it sounds, LifeAtRandom is right in that #3 is the most canon-compliant (especially because of what we know of Lily). James/Lily has become one of my favorite 'ships, but I'm always dismayed with Marauder-Era fics that use jealous!Lily because for it to work, she seems to be drawn so far OOC. I'm sure there's some kind of drama (there is a war going on outside Hogwarts), but being a teenager is drama enough, and if Sirius and Remus are to be believed, James just needed to grow up to win Lily over. I think she's to vehement towards him because she actually does like him; he's smart, funny, and loyal to his friends, and I think she'd definately consider those good things, but she'd be turned off by the immature arrogance. I see their getting together as a combination of his maturity, them having to work close as Heads, and a general thawing during sixth year that paves the way for a real relationship seventh year.