Gary Neville's attempt at the Valencia job suggests he perhaps needs to learn the ropes in the Championship or something before having another go in a top league.
Howe would be a good fit IMO, though I suspect that convincing him to break his contract or convincing Bournemouth to let him go could be difficult and take ages.
Flores might be ok, but Watford's drop in form in the second half of the season suggests he might be a bit of a risk.
De Boer? Done well in Holland, appears that he wants a job in England, but untested outside Holland.
Sampaoli? Could be brilliant but I'm not sure we are big enough to tempt him away from international management.