Another possible option: If you press and hold the Shift key early as the guest boots (i.e. when the VMware logo is still on screen), you should be able to boot the VM in Safe Mode. If we're lucky, that may bypass the vmmemctl driver and allow you to boot the VM and uninstall Tools. I have no idea if that will actually work in the middle of an OS upgrade, though... Perhaps worth a try...
Cheers,
--
Darius