I dont know if these work well in Podman, if yes this may be unnessecary.

But I think as a "virtualization OS" it would be great to have these packages preinstalled.

Gnome-boxes Flatpak has no devices support and because of that you can't install Windows spice guest additions. No device support of course also has other problems.

virt-manager is the known and powerful but easy to use Manager, and inclusing qemu qemu-kvm and maybe more dependencies would make it work.

At the moment I layer it and it works great.

Note: Polkit requires a sudo password prompt opening virt-manager. This can be toggled off and should by default I think.