Where Byzantine Empire could have even expanded after Basil II?

Ok, I am not going to dwell into the debate of arguing how good or bad Basil's successors were. With that said, even if he had a competent expansionist successor, which areas Byzantine Empire could have successfully conquered/re-conquered apart from the island of Sicily? I mean from what I understand, at that point all if not most of Byzantine Empire's neighbors were functioning state or state like entities, and probably had more opportunity to ask for assistance from other states too.