My picks assuming that the very best are off limits:
Giggs: Knows what it takes to win, and as a winger could possibly get the best out of Richy and Lookman.
Arteta: Still a blue, no matter how long he's been at City, can see the other side of his 2011 departure now. Connections with City only a good thing. Most realistic option.
Lopetegui: Out of work still, blew it at Madrid so won't be all big time like Koeman, using EFC as a stepping stone to the big time. Connections to La Liga could be useful, as long as we're not buying crocks from Barca for liberia's deficit.