@diskdiddler I'd like to know the same, but haven't had a chance to dig into the project.
I've finally got a stable 2 cpu VM running with it, but it took a lot of work and the magic bullet was Windows 10.
Some of the configurations out of the box like virtualbox had would be nice (i.e. a wizard). I'm a full stack developer, so it might be fun to build a plugin to more easily modify the configuration through the GUI. The current set of tools work, but I had to manually set up my bridge connection and change some other config to make it stable.
Hardware pass-through would be nice (especially for tuners in my case). I'm not holding my breath on that one, however. FreeBSD is pretty type-cast as OS roles go, we all know that it's known for stability and reliability. It's definitely on my short list of OS choices for any service-based server build. (silently sheds a tear for Tru64 again, lol)
Aside from that, I've no clue about the nuts and bolts of building a hypervisor from scratch.