Some interesting thought experiments there!
We have discussed many of these things over the years.
One was creating an audio player people can embed on their sites (just a hard one to get out to the masses without someone else to dedicate themselves to it). Promoting anything to do with independent music IS HARD AND VERY VERY TIME CONSUMING!
I don't think making SB in game only would work for the free to play players I have always said need to be catered for. Many will not want to use Music Promoter and they should be allowed to farm SB to sell if it is helping put some food on the table.
It could help the SB price long term however my head explodes trying to think about all the ramifications!