nice to see some mentions for my first choice to approach, Cruyff; genius football mind, beautiful football, and Barca's most successful manager; also in talks in recent years to manage the Dutch team, but for whatever reasons they couldn't hammer out a deal. Damn that would be an incredible appointment (with whatever management team he'd want to bring with him) and I think we'd truly be looking forward to seeing something very special there, which would really fit with our 'project'.
if he's not available, then probably you could consider a whole bunch of others, like Van Gaal, Hiddink (be funny to steal him away from Chel$ki and perhaps even Russia), Rijkaard, Mourinho (although not my preferred style), Jol - if he really wanted a fast track return to the Prem, Klinsmann (who I wouldn't mind because I think he has some decent ideas and for the first time he had me supporting an attractive German team) and even Sven, who I think basically got screwed by Toxin. Right now I'd take him in as a caretaker for the rest of the season a la Hiddink.
there are many other well-qualified managers in addition to the above, like Mancini, so I really don't understand anyone who'd be worried about finding a decent replacement, or us being able to attract one. Worst outcome is they'd get a few more million in their bank account. I could live with getting sacked for that, no problem.
I should have been educated to be a football manager - best job in the whole world I think, even if you get an early bath!