The more convenient way to handle emergency updates is with the incremental update feature. You can add errata or RPMs from main repositories to content view versions directly with it. It will create a “point-release” of the content view version with your added content.
There is a bug around incremental update right now unless you’re using content view filters: Bug #34357: Incremental CV update fails with 400 HTTP error - Katello - Foreman
Related thread: Unable to publish an incremental CV update - #6 by lumarel
We’re working on it right now so it should be addressed soon.