Thanks for the feedback! Right now, if you modify the permissions on the Core Library file, you should be able to get the behavior you’re looking for. If you give edit access to the main file to your approvers, and give everyone else View access, the viewers will be able to create and modify branches, and the editors will be able to merge them when ready. For now, branch creators will have to let the editors know when their branch is ready for review/merging, but we’re working on a Review feature that would allow this communication to happen all inside of Figma.
We’re of course continuing to listen to feedback around these flows, so let us know if this works for you!