To recap all the info I collected so far on this:
The most straight forward technical way to get MorphOS running in the VM would be to adapt QEMU with a gfx card virtual driver for a supported MorphOS gfx card (SIS would be easier than radeon).

Of course this would only be a first step to boot the OS. As reported on the other thread the licensing check would be problematic on its current form and additional work would certainly need to be done on the virtual drivers. The speed would certainly be limited (maybe less if running on a PPC host ?).

The interesting point is that according to my understanding most of this (except the license part) could be done without changing MorphOS.