One of the early beta cluster goal was to allow to test MediaWiki changes prior to production.
Currently, if one writes a patch for operations/mediawiki-config, it must be merged to master to test it on the beta cluster.
We need a process to allow people to test their config changes at writing time on a part of this cluster. If the process could be automated, that would be awesome, but we at least need to manually allow that.
That would have a real impact to reduce prod breakage due to changes to CommonSettings.php.