But under the new system, all of my child items have to be copy if I want to give the new owner the ability to make copies -- not just scripts, but prims, sounds, animations...
The problem here is that to copy an object you need to be able to copy everything inside it.
Even if you make them no-copy but have a way so it can be infinitely rezzed from inventory is essentially allowing the person to make a copy, blow it up and salvage the pieces and then yoink the animations or whatever.
I don't know if being able to remove object contents currently falls under mod or not, and I can't think of an instance where it shouldn't, so that might be the solution.