If we are not using the guest OS and Windows back and forth, maybe a live USB is a better solution.
It's been live USB for me for over a decade now, and the hardware for fast boot times has finally arrived with USB 3.0.
It only takes less than a minute to reboot to a different OS using a Bootux Multibootable USB stick.
PC does not even have to contain a HDD.
I've used VM's but there ain't nothing like the real thing baby ;-)
Native BIOS booting to active partitions is so fundamental, and now so potentially disruptive that it had to be replaced by UEFI if nothing else just to put some hurdles in the way.