Hi i'm Simone form Italy,
i've found an empty din case like this http://www.italtronic.com/prod.asp?seg=2&cat=3&prod=21
sell from an italian store.
I'm also a system integrator, i work with knx but i'm new in raspberry wolrd. I was thinking the same thing as you: building a kns server but sincerely i have to figure it out yet.
Do you have already posted a discussion in the forum to show us the evolution of your project?
It will be great.
I hope my link was usefull!