Criscito has been playing as a LWB in Genoa for some time now. Not sure if he'd suit into a 4-defenders formation as a CB, seeing as Gasperini doesn't even use him as CB in a 3-4-3 formation now and he doesn't seem to have grown much stronger physically during all this time away from Juve.
On the other hand, as a LB, he's very different to Moli. I'm afraid Ranieri wouldn't give him much trust and confidence as he did with Moli, not to mention we have De Ceglie, whom I don't like as a LW/LM.
IMHO, Ranieri has put so much trust in Moli because he really thinks he has the potential, not just because he has no other options. Ranieri strikes me as someone who considers energy and physics far more important. He likes players who run a lot, even if they are not very effective nor skillful. Criscito is more technical than physical thus I don't see him with a bright future with our current coach.