I'd like to see Necromancer added as a playable job. The lore does not and has not stayed rigid on many fronts, so it's not as if the story couldn't evolve to allow for it to be acceptable within Eorzea. With that said, presumably the story is eventually going to move on from Eorzea and take us further afield.

Aside from Necromancer being present as a job in at least one Final Fantasy game, it's present and playable in some form in at least two of the other major MMO's on the market right now. Namely Elder Scrolls Online and World of Warcraft. As someone who greatly enjoys playing darker jobs/using questionable powers for the greater good I think it'd be brilliant to allow those who want to do so to have more of that as an option.