I'd say it's not possible. Patches are defined as changes to configuration files (like, which file is changed and in what way). You can't make a patch that unapplies all other patches, because you don't know what changes other patches have done.

It would be nice if Patchmanager had a command "unapply all". That could be done. It would just unapply all the patches that have been applied, one by one. You could use that before a system update. And similarly there could be a command to re-apply those patches after updating.

But no, there can't be a patch to do that.