Virtual Acorn does not give virtualisation, it is emulation. i.e. It runs on top of a host OS replicating a limited set of legacy hardware, where as virtualisation gives you shared access to the full native hardware. Its an important distinction, and the difference between being a dead toy OS, and a proper operating system. If RISC OS is going to run on non ARM hardware it has to be on top of a virtualisation hypervisor, and not dependent on any other OS as an emulator is.