You are right, Celtic or Rangers could be an options there but would such clubs ask him? Seeing that last months he is spending between Italian and English Serie B, I can't see what could he offer to either of clubs.
About Czechs, hard to say. Hable seems to be an disappointment, coach of Czech U19 keeps on telling that move to Fiorentina did bad to him, and that he is worse than he used to be. And I believe except the summer when he joined, he never got the chance to train with the senior squad. While Mazuch could be having some future with us, Ujfalusi always speaks very nicely of him and his qualities (although he could hardly tell the press that Mazuch actually sucks hard)...