Re: KVM is making QEMU shoddy
A good response to this is that QEMU is kept under Git source control. One can get the "last known good" build (without KVM), fork it into a new branch, say "QEMU Legacy", and develop onto that.
That's how many open source projects started ... fork for keeping legacy compatibility (MATE started as a GNOME 2 fork in response to GNOME 3).