No, that’s the tricky “taking the piss” stuff that would require more than a forum post to sort out. But I would absolutely make attribution and transformation the cornerstones of the system. Satisfy those, and you’re in the clear. It involves some trust that this system will be used fairly - e.g. attribution is clearly given, so in this example the original library music artists are credited and gain exposure - but the current system, any any system, has the same constraint.
In practice it obviously gets murkier and more complex as you try to thrash out the finer details, but this would still be my starting point. Of course people can already invite this situation by using a Creative Commons licence for their work, but there you’re inevitably giving other people the right to redistribute the full original work, which is a bit beyond the right to sample.
The key here is, you need a way to differentiate sampling from plagiarism. Not easy, but still worth thinking about.
Edit: won’t take this any further here so as not to upset anyone, but happy to keep going on and on in a separate or new topic.