[crucialfelix]

>> something like Ableton Live, musicians could literally share/stream their workflow and assets for people to toy around at home

Ableton have built this: https://blend.io/

Note the remixes competitions listed further down the page. AFAIK it doesn't have much traction, although I think their execution was very good.

There have been quite a few online collaboration products built into sequencers. Rocket Network back in 2000: http://www.1000tracks.ru/remembering-rocket-network/