Little back story. When you grow, and may grow over few hundreds, event PB of backup data, the pressure of not putting a repository extend in maintenance mode and doing a evacuation gets more demanding, as just by putting a repository extend into maintenance mode - you are basically putting it offline and all backups that depend on a point in an incremental chain will fail. (or do a new full if you have configured it that way)
Doing an evacuation of a extend, with 10-20-30-40-50-60 TB of data takes time, even if you have multiple 10GB links between repositories and you will halt a lot of operation just by doing so.
So we need a new option, pause all new writings to a repository extend and let all incremental expire over time. (months-years), and in the end, the health check/defrag process could defrag the fulls to a new full in another repository extend.