A whole afternoon playing around... ok, no, that's not the word... It's been a whole afternoon banging my head against the wall that libvirt and its cousin virt-manager are.
I ended up going back to the ol' trusty shell script I use to fire up my FreeBSD and OpenBSD VMs. This is a desktop, not a server, so the VMs are on just for what I need to run on them (mostly checking portability of code I write) and then, they're shut down. No need for a socket listening in the background or a service to do who knows what.
The thing that really pissed me off was the permissions situation libvirt/libvirt-qemu got me into. I mean... wow, it silently set an ACL entry on my $HOME on its own to unilaterally give itself permissions inside my $HOME. Wow.