KVM supports Windows just fine, which is why you can run Windows on GCP and Openstack. And Firecracker seems to support enough of a machine to boot Windows as long as the windows instance has support for libvirt disk devices and a libvirt NIC.

However, it seems they boot in a slightly unconventional way. They take a elf64 binary and execute it. This works for Linux and likely some other operating systems that can produce elf64 binaries. Windows supports legacy x86 boot and UEFI, but likely not elf64 "direct boot".

So if you can get windows into an elf64 binary and have it run without a GPU you could have it boot. So, likely not. But the reason isn't due to KVM.