Keepers
I'd keep one of robles/stek (can't decide which, maybe robles because of age, but stek is more reliable and would love to see us get begovic and pickford to battle it out for the no.1 spot - Pickford being out future long-term keeper.
Defence
Coleman, kenny, williams, mori, holgate, galloway, baines
Midfield
Mirallas, Deulofeu, Gueye, Davies, Walsh, Barkley, Besic, Bolasie, Lookman, Tarashaj
Strikers
Lukaku, DCL
That's 17 first team players with possibly a couple of youths to come through.
I would consider keeping Jagielka, McCarthy (our best hope of raising a good sale), Lennon (can't believe he's only 20!) and Barry as squad fillers and a bit of necessary experience.
However, most of them would not be in my starting XI; as well as the two keepers i mentioned above, we'd need a new left back in the summer to properly push Baines, we obviously need a new dominating centre back, we need a new DM to replace Barry (hopefully schneiderlin), we would need 1, possibly 2 new wingers (i'm just not sure on lennon any more, whereas mirallas and deulofeu could provide a tad more class), as well as two strikers, ideally one who can also play as a playmaker.
And that has us around that 25 player mark including a couple coming through from the youth which aren't included.
That sees a release over the next two windows of:
Robles/Stek
Oviedo
Garbutt
Browning
Pennington
Gibson
Cleverley
McGeady
McAleny
Henen
Niasse
Valencia
Kone
Rodriguez
and possibly:
Jagielka, McCarthy, Barry and Lennon as well as Tarashaj, Grant and Dowell (who are al young enough to have more of a chance imo)
Think that's a decent overhaul over the next 2 or 3 windows.