Not really been all that impressed with Fortune. Had a poor season so far and, after a bright start last season, he wasn't much cop for most of last season either. Hence being dropped back to play U18 football and even then he's not a guaranteed starter at that level.
If you want to talk about U18 talent at the club, have a look at Emile Smith-Rowe and Trae Coyle - serious potential in those two.
Of the more familiar lot - Maitland-Niles, Jeff, Willock etc. I'd say Nelson is hands down the most likely to be able to step up to playing proper football in the first team. He's easily got the most well rounded and mature game. He's just very good at nearly all things and has a couple of real standout attributes.