It’s not a bad idea to keep the previous couple of release versions up on the site just in case.
If the reason you don’t to that is because upgrades may change rig data making downgrading not feasible then maybe a good feature to add to the rig manager would be to - have it make a backup of your whole system locally to a subfolder as it upgrades and allow rollback that not only installs the older OS but installs your older rigs.