The “safe rules” concept is a little strange indeed, not very consistent.

I actually agree that for an MV3 ad blocker I’d better have a fully declarative default (emphasis on default), but I’d like to provide an option to grant more permissions and allow more rules. I’ll wait until declarative cosmetic rules become a thing before going this way though.

What I don’t like about your way is that it’s very difficult to use the MV3 version for filters development, filter list authors will have to re-build the extension every time they make any change to the underlying filters.

Maybe this is not a big problem though, we’ll only see it when MV3 becomes the only option and there will be more issue reports from its users.