When I read of your predicament, I too thought about a VPN (I use NordVPN but I don't think it much matters which), as it tunnels through my office NAT effectively. But that's on local PCs. The problem I couldn't solve for remote PCs is--if something messes up at the remote PC, how do you re-establish access? This isn't a problem if the VPN is running on the local computer because you can just kill or restart the VPN. But for a remote computer, it seems to me that if the VPN breaks you may just have no access. I personally would want to try it on a spare test laptop before I committed for my observatory PC.