It sounds as though you have some other kids playing in your sandbox who may also be throwing sand at you. Hopefully you will make some headway using your ownership of the brand to justify your cause, but your brand doesn't make the rules, Amazon does. I am assuming by "merged" you are referring 8 items that are combined under a single variation parent. Is the variation justified, meaning are they reasonably similar items?

If these have retail (1P) contributions, you may have an uphill battle as on the vendor central platform Amazon has moved to an automated variation service (AVS) where Amazon is using similar product attributes to automatically create variations.

In your fight with the brand registry and RBS teams on the variation, I might focus less on demanding how you have rights (debatable), and instead focus on how the variation(s) in question are invalid and will create customer confusion and preventable returns.