Greetings,
How does your "own modified" Warcraft differ from the normal one?
It must've been something great, because otherwise it's like risking with a less-known video codec.
Either way you choose to go with, I'm not going to download another GB worth of file size to my PC that's already in the between of fast and slow. At the moment, loading the chapters takes 7 minutes for me already, so if nothing's gonna happen to reduce the file size, I fear the campaign becomes unplayable for the high risk of crashing.