True it would be interesting to know how well WSL works.
And some of the complex multiple network device configurations, I had iohyve administered virtuals with a backend filestore network as well as a front door.
Iohyve used zfs environment vars embedded in the FS to hold configuration which was clever, arguably too clever.
The problem with nested virtualisation is that it isn't fully hardware accelerated. The missing features (shadow paging, etc.) have to emulated in software. Such emulation requires lots of delicate error prone code.
Otherwise, a super and very complete guide. Well worth bookmarking if you want to do virtualised os on FreeBSD.