I’m fairly confident this is impossible. But am breaking apart a brand, with some products moving over to new brand under same corporate entity.
saw self-brand hijacking was a trick, but doesn’t seem very TOS-eee
lol
Just putting this out in the universe I guess.
Can be done if you still had SAS. Did it with SAS myself TWICE…
Brand name changes can be done with SAS.
Here’s the story:
Due to TM issues, set 2 items up under our company name instead of the actual brand.
TM finally went through after a multi-year struggle with the USPTO.
Changed both listings with SAS to the brand name. Easier because the brand name was on the packaging. Unsure of what you’re using to justify the change on these products.
DIY, without SAS, would seem pretty difficult, if not impossible as you noted.
i had a feeling SAS would get brought up here. 
GS1 is your friend - it is not impossible (albeit difficult on certain scores if the ducks aren’t correctly aligned in neatly-ordered rows, even if you were still using SAS Core. as our friend Steve alludes upthread) to achieve what I perceive to be your desired result.
Nevertheless, I’d recommend - again - that having a legal eagle/beagle on retainer is probably applicable for your product-line of goods.
You bring up a good point about GS1… You can edit existing codes for Brand Name on GS1.
I know others have said that’s not possible but we can do it with our Prefixes and we aren’t special.
Sorry, didn’t mean to rub salt in your SAS wounds. Just sharing an experience that was actually positive with Amazon / SAS Core… 
We did this once way back in Brand Registry 1.0 it was just before 2.0 and USPTO office were a requirement. The change was not easy, the Brand Registry Team were very helpful to us. Ahh, good old Amazon domestic support.
Our need was due to one of our vendors, not “liking” our Brand Name. After $25K it was clear they had more lawyers and money than we did. I was very grateful for Amazons help in the change.
I do not think this could ever happen again.
However, without naming anyone, one of our very long suppliers, looked the other way when the largest distributor they had changed long time established catalog pages. That we actually created. They changed the brand from the manufacture to their name.
It was not worth the fight for me. I just sat back and watched it happen. This was in relatively recent times. The original catalog pages were done with UPC codes we owned (Yes it was/is a thing by the original court case) and yes it was allowed by Amazon at the time. Somehow the seller used that to change the brand name.
If so I think the concept of leveraging your ability to change the brand in the UPC rental registry (GS1) may work.
Any update @casbboy ?