Z's (or Hogwarts's) revenge on Snape are hilarious and definitely worthy of the son of a Maurader. (For that matter, I suppose Lupin could be behind them, but I doubt it.)
I really liked your well thought-out ways that Luna's vision might be fixed. Having three possibilities and using at least 2 in the short term was very interesting. I like the idea of a Muggle organ donor working for the long-term solution. It's something most authors wouldn't have considered.