yeah beatport tried and failed to get into streaming a while back too.
Pledge music and indeed Patreon are both doing good things for unsigned artists and I see potential for some crossover.
One of the major problems with beatport, is as they are the biggest and oldest store for electronic music, they take 50p on the £ and will only deal with "distributors" who generally take another 30% or so just for uploading your music. which leaves the label with roughly 35p in the pound to split with the artists. which is a terrible deal.
Also they don't offer any kind of promotion except for the charts. which are rubbish too. if an artist has a release, they will make a chart and put a few of their friends tracks in, it doesn't help with discoverability for most independents. the only thing which really helps sales on beatport are a banner. and that is curated by a person who works at beatport. which is flawed.
So yeah, in my opinion nobody out there has nailed it yet and there is still opportunities in this area. I'm confident that if you offer a service which is beneficial to independent labels and DJ's then they will use there social media influence to push fans to buy from you rather than beatport/itunes/etc. It's not a unicorn, but I believe it could easily be self sustainable (I'm hesitant to use the word profitable, as I'd rather it was profitable for the labels & artists than the platform, as long as the platform didn't lose money of course).