Would it be possible to setup any type of authentication key with WinRM that would be similar to the way SSH Keys work? I don't mean just the encrypted transmission but more to be able to automatically authenticate with several servers which cannot be on the same domain. I'm trying to avoid having to create numerous accounts across all the servers.
You can use Certificate authentication to get a similar result but you will still have to map local accounts on those servers (or in their domains) to the certificates. There are some pointers available here.