I have long wanted to build a combination of: Bandcamp, GitHub, and Steam for musicians.

Basically, a platform for musicians to produce music (and associated videos, artworks, etc), managing their assets securely, sharing and collaborating; then engagement with fans, promotion, merch, and touring support; and finally a simple platform for sales (streaming, downloads, and physical good) where the store takes a reasonable fee, but the bulk of the revenue goes to the creator.

I was kinda hoping Bandcamp would evolve in this direction, but I think that's not likely now.