It's obviously not going to be Conte, Agnelli would never take him back. For me, it's either Poch, Inzaghi, or Allegri. I don't see Zidane leaving Madrid yet. If he does, he would be my first choice for both mental and tactical reasons. I don't think that any player would take anything for granted and we would certainly not see a shameful lackluster performance like yesterday's with him at the helm. Inzaghi would be my last pick. Between Poch and Allegri I would still lean towards Allegri simply because of his proven record and because I truly think he still has some unfinished business here. With the players already acquired and a few more acquisitions i actually see him doing really well here again. Having said that, I would definitely not complain if we end up with Poch.
Above anything, however, please do not throw Pirlo under the bus by putting him in front of this group. Let him develop his managerial skills without much pressure and one day he'll hopefully be ready to take over.