Can EPiServer CMS 6 (or any other version) be installed on Windows Server 2008 R2 Server Core?
Yes, EPiServer will run on Windows Server 2008 R2 Server Core. I did a quick POC, but had to install SP1 getting it to run.
If you'd like I could assemble my notes and put together some sort of howto. I encountered a few tricky error messages.
I went ahead and wrote an article about it. You can find it here: http://blog.mathiaskunto.com/2014/01/25/how-to-install-episerver-on-windows-server-2008-r2-server-core/