BBrawl has a code to not only replace Hanenbow with the Wifi Waiting Room, but also to redirect it's music to the Waiting Room's as well.
Effectively, when you choose Hanenbow (On Vs Mode only) the Wifi Waiting Room and it's music loads, and is indistinguishable from the real thing, with the exception being that it spawns Sandbags based on your item spawn preferences. No items means no Sandbag (except maybe the first).
That being said, when I replaced the Waiting Room with one of the SSE stages, it loaded the SSE stage as well (the one with the swirling tornado thingies in the background).
Altogether, frigging spiffy! :3