This is good stuff, i quite enjoyed it.
I also see a great many opportunities for what is about to happen, a good potential to evolve and a clear, logical diversion from canon. That last part is quite rare, normally things just randomly change at some point of choosing, having a massive occ moment for plots sake, but you managed to make a straight change without any moments of occ. Perhaps aside from Krum? But i don't really know anything about him, so you could easily convince me of anything there.
Author's response
Thanks. The change to Krum is important later on. For the rest, I appreciate the words. Laughing at the "OCC" plot changes.