Who wants to help? ^^
Installer like in “Debian Installer” i.e. some iso which installs a Whonix system including the host with some user interaction?
If not, how should this system be setup?
It’s more like “who wants to implement it”? 
Why an iso?
sudo apt-get install whonix-virtualbox would be cool. (No chance to get that uploaded to packages.debian.org.)
You know what’s mess nowadays? Adding a third party (such as the Whonix) apt repository to your Debian system. Awful usability.
There is apt-add-repository but it modifies /etc/apt/sources.list rather than adding a file to /etc/apt/sources.list.d. And the signing key still has to be somehow added. More tinkering. Do you think you could contribute upstream to apt-add-repository to improve that?
Ultimately, if Debian users could just type “sudo apt-add-repository whonix” and all would be sorted, that would be great! Then it’s just “sudo apt-add-repository whonix” followed by sudo apt-get install whonix-virtualbox and be all set.
Most or all of the time I came into contact with the Debian installer were the isos for installing Debian.
What would “sudo apt-get install whonix-virtualbox” do in the end? Set up a complete host system or just download and import the VM images?
It probably can’t setup the encrypted system as described above. At least not on the system where it is currently running.
Right.
It depends on the goal.
Install virtualbox and download and install Whonix VirtualBox VM images on Debian Linux.
If it’s supposed to be a full Whonix host operating system, live and/or installer, then an iso installer makes sense indeed.
I already did half of the work when I drew this picture. ^^
Whonix for KVM will be distributed with the distribution :).
We will name this project:
“Whonix Standalone”.