KVM virtual machine image download support is already supported by the installer.
Other KVM support for KVM import etc. is not planned to be implemented by me. KVM support would need to be added by the maintainer of Whonix KVM, which is only you.
This is because if KVM support isn’t added by the maintainer, the KVM specific commands (import, re-import, network setup) done by the installer versus manual import will always be clouded in mystery what the installer actually does versus what not. That is, if there is an issue with KVM, the installer would always be the first suspect as the source of issues.
It might be the installer’s fault or it might not be. But that investigation should be done by the KVM maintainer. And any changes required for the installer, should also be be done by the KVM maintainer.
Especially with multiple operating system support KVM maintenance seems difficult by looking at the KVM sub forums. For example: Unsupported qcow2 feature extended L2 entries
If I added KVM support, it would be almost the same as taking over KVM maintenance, which is too much.
In other words, by adding KVM support to Whonix Linux Installer, you would be effectively “out of the game” for KVM maintenance.