I wonder if the FA would be tempted to give Stuart Pearce a crack? He has after all managed the U21s very well, for a good amount of time. He'd have that understanding and respect from the players.
I would have Pearce as the Asst Manager behind Redknapp with his Spurs team of Bond/Jordan as caoches alongside Ray Clemence as goalie coach + England medical/physio team lead by the great Gary Lewin.
Pearce needs a vital role for the reason you stated the U21 players for the future are his players.