I can only wonder what copyright law might do to such a model. Would patronage allow one to play the artist's music in a public space without prior permission/consent? Think about all the recent political campaigns that used songs in such a manner. Also, I wonder if the patronage model would make it that much harder for an artist to sustain his/her career.
This is just my opinion, but I feel copyright will be less enforceable in the future when it doesn't actually generate revenue. I have to think over time, artists will not want to gate their content, and provide distributors free access to their music to businesses and public spaces in exchange for them, well, playing it and getting exposure. Just like they're doing now with their fans. And all this will be accelerated when people stop buying music altogether. This is sort of a stretch hypothesis, I'm actually not super familiar with how ASCAP and BMI works.