Here's my idea for a Rhythm Heaven stage. ^^
I think a good idea for a Rhythm Heaven stage is for it to have a gimmick similar to the WarioWare stage from Brawl. The match starts you off in the Café, but then after some time the stage changes into a mini-game. Once the mini-game is over you are brought back to the Café. The difference between this stage and the WarioWare stage is that there would be a bigger variety of mini-games, and the mini-games would start at a slow pace. As the match goes on however, the mini-games gradually speed up and the transition between mini-games will gradually become shorter. Once the speed of the mini-games have reached their max, about 20 seconds later a ten second countdown will begin in the background of the stage, and once it reaches zero the background will say REMIX! During a remix the transition between mini-games will be instant, and the speed of the mini-games will be slightly faster than it's regular maximum speed. A remix will last for about 15 seconds.
The reward you get for getting a PERFECT on a mini-game depends on the speed of the mini-game. Messing up once or twice during a mini-game will get you a SUPERB. A SUPERB rewards the player with recovery damage from the previous speed level. Messing up three or four times will give you an OK. An OK rewards the player with recovery damage from two previous speed levels. If you mess up four or more times during a mini-game, not only will you not recover any damage, but you'll also be stunned for about two seconds.
Perfect Normal Speed Reward: Recover 1-7%, SUPERB Normal Speed reward 0%, OK Normal Speed reward 0%
Perfect Faster Speed Reward: Recover 8-14%, SUPERB Faster Speed reward 1-7%, OK Faster Speed reward 0%
Perfect Max Speed Reward: Recover 15-20%, SUPERB Max Speed reward 8-14%, OK Max Speed reward 1-7%
Perfect Remix Reward: Recover 30-50%, SUPERB Remix reward 15-20%, OK Remix reward 8-14%
Some special effects for getting a perfect could be having the word PERFECT appear in big golden letters in the background, hearing a loud applause, and having a spotlight be on all the characters in the match who got a perfect for a brief moment.
This stage is very gimmicky, but I think it makes sense for a Rhythm Heaven stage to be gimmicky. Besides, there's always the Omega version.
The only names for the stage I could come up with are: The Café, Rhythm Café, and Rhythm Heaven Café.