I was thinking of making a new Rock Star kind of game, similar to the band management sims, but with a bit of a twist, when you go to the gigs and have to play, the game becomes more challenging. I'd make it so you either use the Aiga's keyboard (or perhaps a MIDI keyboard if you have the quipment) for playing keyboard music, and a joypad or PS2 Guitar (using a PS2-CD32 adapter) for playing guitar music. Then it'd be similar to Guitar Hero (or Shredz64 on the Commodore 64), where you have to repeat a pattern that scrolls onto the screen, and the more accurately you copy the pattern, the more points you get and the further you progress through the game.
I think a game like this should start off small, you're a teenager who wants to form a band, so you put ads in the paper and interview band members, get the band together, then manage how much they practice, kick them out if they start slacking off, organise tours and stuff, then finally you play on gig night.
Would a game like this go down well with the Amiga community? I can propose it to Underground Arcade and see if we can make it. Perhaps use digitised graphics to speed things up, people could even submit photos of themselves looking like rockstars to be used as selectable band members in the game.