Just add a icon to the vault warning users if it isn't PM compatible that the ULer would specify. IT can be done similarly to the Wifi Desynch icon.
If any existing hack isn't compatible, just report it and it will be up to the ULer to put the notification up.
In my opinion, this wouldn't be a suitable solution.
There's 3 options for Wifi Desync:
Yes (it desyncs)
No (it doesn't)
Unknown (Online play effects are unknown)
We can predict if a hack is going to desync in WiFi. If the bone structure was modified in someway, if a completely different moveset (PSA) and animations were added; these things desync online play. We've known these things for a while now.
If what EternalYoshi says it's true we can't predict if a hack made for vBrawl would work with Project:M unless we test it (something I'm not personally eager to do).
We can't tell how the game would react. Maybe it'll freeze when lucario and mewtwo are in the same match but not otherwise.
I might be exaggerating a little bit on that last sentence but the fact is:
If the final user has to test for compatibility ultimately, why even implement this function in the first place?
Sounds like a co
al waste if time. Just assume a hack was made for vBrawl unless the description says otherwise.
Basically this^.