CoreOS support - I don't even know how to begin this :) but it seems one of the most innovative and greatest Linux based distros for servers https://coreos.com/
Will Virtualmin support CoreOS in the future?
No. Never. I mean not for Virtualmin at least.
I think you guys have the wrong impression about CoreOS. Don't let the name OS trick you. CoreOS is designed to be as minimalist as possible, why? Because its designed to run as a container OS, between that and Rancher and others everyone fights to get the smallest possible Linux distro possible to act as a control host.
The smallest is still busybox. Its 2 MB big. I'm not joking. It's a Linux OS that is smaller than some images online.
CoreOS has nothing out of the box. No package installer (you can't install anything) and has everything stripped down. You can't run anything on it. No web server, or email or even install anything, not one single package can be installed because you are not supposed to use it like that. So Virtualmin and no other control panel or any service will work. Nothing except micro containers.
You realize you necroed a 3 years old thread :) don't you? You are right of course about everything CoreOS - all became clearer for me in the meantime.
Don't take the name of root in vain...