OK, a bit of content is DRMed (audio, video, boss, etc.), and another professional level designer either buys the rights to use that in his commercial level for a constant fee, or the system allows some kind of payment redistribution like a portion of the revenue directly being transfered to the original author.
Is this the generalization you have in mind?
Because I'm not sure. Alternatively system can bypass any agreement between content owners and let the user buy the optional second content (like audio) in addition to the first one.
Or are you talking about simply just letting level designers DRM arbitrary parts of the level? For example a guy may be very proud of his music and only wants to protect that, while keeping the rest editable and sharable?