I would have been a good use case, but unfortunately no, if your key was registered it would be left alone on all servers (though you had to place it, and acces

I would have been a good use case, but unfortunately no, if your key was registered it would be left alone on all servers (though you had to place it, and access control was done by way of bastions). Ssh certs weren't used because the system was put in place before they became commonplace.