Thanks for writing this summary! I think the changes you’re proposing would be an improvement on the current situation, as the labels would more closely match the imprints on the releases. I’ll make one point though:
For the earlier “Resonance” releases like this one, I don’t think I would enter the Label as “Deutsch Grammophon Resonance”. If I had that CD in my hands, I would enter “Deutsche Grammophon” as a label since it appears (by itself) on the CD label. I would also enter “Resonance” as an additional label since that’s what it says on the spine of the case.
Now, there seems to be disagreement about entering more than one label on some releases, but that’s what I’d do in this case.
My point is that if there is a Label “Deutsche Grammophon” and a Label “Resonance”, I don’t think it’s necessary that there’s also “Deutsche Grammophon Resonance”.