The biggest question is: does Apple want to bring back the Xserver? If yes, there are several ways. If not, no good proposal will sway them :)
But one thing was interesting during the AS announcement at WWDC. Federighi stressed how good a hypervisor macOS is. That was probably first of all a comment about virtualization on the new Macs, but could also allow to install any operation system as guest on a cloud server. Many cloud services are running inside VMs.