Thanks for sharing. Just for reference, there are few major modes out
there implementing this kind of approach:

http://www.emacswiki.org/emacs/MultipleModes

For example I have used mmm-mode to good effect in the past, to
auto-switch between HTML and Perl:

http://mmm-mode.sourceforge.net/

Thanks for sharing the alternatives. The proposed solution has the charm to use only a minor mode which consist of less then 100 lines of lisp-code. I thought if it is of general interest, it might be easy adoptable within org-babel. I would prefer to use org-mode as major mode.

Best regards

Torsten