you could just swap the file, but dont do this when you currently dont have another option around to boot this machine into whatever in case you need to revert that.

That's fine, it's a virtual machine. I was actually running 9.2.2 on this VM (I can't remember how or when I did update). In my tests I have noticed that there is no benefit at all for me to run this VM with a newer MacOS ROM. QEMU does not grab the mouse when I move over the VM screen when using the newer version; I had to tell QEMU to do it with a keystroke. So I reverted to my backup with the older rom (8.7) and decided to stick with it. "If it's not broken..." ya know? But thanks anyway!