If the fee was reasonable then i think that it would be sensible to sell him as he's on reportedly big wages and you could replace him with a player that excels in the number 10 role or as a striker. However, it's clear that Van Gaal likes players that can play in different positions if needed, he seems to be a big fan of versatility. It's going to be tough for Fellaini to get a chance though as much as i like the big fella. CM is pretty much a no now considering your options (Bastian, Morgan, Carrick, Herrera, Blind, Di Maria - although Di Maria may leave and Herrera plays a little further forward) and CAM is very difficult considering you have Januzaj, Mata and Herrera. Basically you'll be paying him a hefty fee to be sitting on the bench for the majority of the time in my opinion. Hope he doesn't leave though, United are the team i watch most outside of Everton and i love the guy.