Really exciting to see this manifesto.
There's already some existing co-operative music store/bandcamp alternative projects that are selling music and accepting new artists.
https://jam.coop is the one we are building. We launched last year in response to the sale of bandcamp and the uncertainty we felt in our communities of musicians who depend on Bandcamp for some or part of their living. In contrast to subvert we've decided to take an incremental approach. We're incubating jam inside an existing worker co-operative, building the features that our users need, and working towards an "exit to community" where jam will become a multi-stakeholder co-op owned by artists and workers.
I'm also familiar with mirlo and ampwall who are working on similar projects.