There may be technicalities that prevent this, but ...
It seems to me the limitation comes from the PSN Store and how quickly you are allowed to place content there. It can't be just distribution of the content, because games like Little Big Planet have tons and tons of user made content available for download but the advantage they have is it's all free so no need for the store.
So ... instead of putting all the RBN songs on the store, why not just put in one item where you can buy some RBN credit (or perhaps several items at different denominations) and then you can use that credit to purchase RBN songs?
Just a thought ... hope it's not too dumb of one .