You can use qemu for pure userspace emulation, without passing /dev/kvm. It'll be slow. Probably unusable for Windows. However I used this kind of emulation to build images with qemu from arm host and it worked OK, like few minutes to boot from Linux image, install some packages, run some commands and shutdown.

Docker is actually great for that kind of applications, because you can run it everywhere: Mac, Windows with one single-line. The only problem is that it's not very convenient to use docker images just as file containers, but it works.