Before I start I would like to say that I'm not skilled in Photoshop or anything like that so I can't put together mock ups of my idea but Hopefully I can explain it and give ideas well enough.
So I've played all of the Project Diva games, love them all. However I got thinking: What if Osu! had a Diva-esque gamemode? Project Diva itself is fine but there aren't really a whole lot of super challenging songs, and people are usually left without a few songs they would like to play. The community would be able to create maps for their own PjO! games as well as enjoy songs that they would never be able to play otherwise in a Diva game. (i.e songs that aren't Vocaloid ones)
The already existing Osu! standard maps could be easily converted into PjO! maps using the same idea that Osu! Mania or Catch the Beat does. Every new combo is a note switch, (i.e going from Cross buttons to Squares), rollers become held notes, and hits will become single notes.
Finally: The game itself uses PS3 controllers. However Osu! does not currently support hat switches (the D pad) being used as bindable buttons for the game itself. If people wanted to play the game with a PS3 or Diva controller, they would have to use an external program such as Joy2Key, or the game would have to be updated to allow this.
I really don't have much else other than a basic idea but I hope you guys enjoy the idea! Thank you for reading the post!
Here is an example of Project Diva Gameplay for people who would like an example of what I'm trying to get across.