If you check out the Y-Wing entry on wookieepedia.com ( http://starwars.wikia.com/wiki/BTL_Y-wing_starfighter ) it clearly states that the Y-Wing used proton bombs and was an assault BOMBER. As well, in most Star Wars games and RPG material, the Y-Wing can drop bombs. So, why doesn't it have a bomb slot? And what about a crew upgrade slot since it did have a gunner?
Maybe the Y-Wing needs a new card that allows it bombs and a crew upgrade slot.