The ability to disable add/remove for Blocks and Layouts via blueprint

For example, when loading a different blueprint per user role (https://getkirby.com/docs/cookbook/security/permission-tricks#completely-different-blueprint-sets-per-user-role), it would be useful to only only allow Admins to add blocks and change layouts, whereas Editors can only edit the content.

I think this would also alleviate the need for a visual Blueprint Editor in a way, because you could essentially build entire pages via the Layouts field then lock it down before sharing with a client.