Don't they do song switching for Wifi Training's NES song? Does that cause desynchs? (wouldn't know, haven't tried BBrawl online before)
Custom stages is also a high priority for me as well. Although there aren't too many I'd recommend. Definitely the edited Jungle SSE stage that Brawl+ has (which has more restricted stage boundaries so they aren't so huge), and another I can dig up from one of the threads that someone made and applied heavy editing to.
Otherwise, many of them would still need to be edited for tourney play. Most of them have gigantic stage boundaries that make them quite annoying.
I say make sure it's done using Phantom Wings' method where you can have custom Stage Select screen icons as well. Just to make it easier. Oh, and a Wifi icon for Hanenbow with a Wifi picture/name logo on the left as well
I believe all of that's possible.
This sounds like it's turning into a lot of work, but this is the kind of thing I think the community could help with to lighten the load on the BBrawl developers (gathering codes and textures and whatnot), and I think it'd definitely help BBrawl get some more exposure. There also shouldn't be TOO much work to be done by the BBrawl developers for the next version, as from feedback received, it doesn't sound like there are too many major edits to be done to characters.