One point about the Antioch thing, yes I was informed by BG that he couldn't reach Antioch in time but what if things were such that he COULD have. I think that would have a better chance of tamping down some of the crusader hate that resulted upon learning that he turned back.
I think Myriocephalon was overrated. Manuel only had a few years left but the Byzantines still
won in 1177. I'm not sure how much could have been accomplished if manuel had won in 1176. Had Manuel been followed up by someone competent, advances into Anatolia could well have continued but as we all know he wasn't.