We have similar scenarios. A service broker catalog may change over time. Removing and changing plans is tricky, but must be possible. The simplest use case is correcting a typo in the service description. To deprecate a service or plan, it might be necessary to change the bindable flag from true to false at some point.
Adding new services and plans should be straight forward, though.
I guess some trivial catalog changes don't need admin consent. Others might be serious but important. It doesn't help if CF thinks a plan is bindable and offers it to the user, but when it tries to create a binding it get an error message from the broker.