I'd really love to see a hypervisor that emulates IPMI/iLO/AMT/whichever flavor management hardware on machines that lack the capability. It should run a single VM only, and pass through all other hardware, but also cordon off eg. a single TCP port, and allow the user to power cycle the VM, along with remote control (could be done through VNC). Bonus points for exposing temperature and other sensors.
But when that hypervisor fails to boot you are SOL. I have vFlash cards in all my Dell servers with the OS install media and a recovery image so I can fix broken installs quickly. Oh, and that stupid PCIe training error from a NIC that went bad would have required I plug in my monitor as well.
It would be useful, but why not just run VMWare or Proxmox at that point?