Hi Genevieve,
As far as I’m aware there aren’t any new developments with editor permissions since this post here. There’s a lot of growth in the area of Workspaces however that’s different.
In your situation, you’d likely need to build a subsystem for managing that editorial access. It’s a fairly technical endeavor, however Memberships + external automation like Make.com are a pretty good combo for building this. Soon you’ll be able to use Logic for this, once it supports CMS ref fields.