Super smart idea, and sounds like it would be entirely possible!
...but I'm not sure I'd like that, the possibilities are huge for sure, but so is the potential for confusion and overwhelming patch complexity!
I think a lot of the things I'd like to do by combining two is already possible by routing external signals to both and mixing/routing outputs via the patch points anyway.
Perhaps 'some' cross patching of critical internal stuff might be useful, but if these parts are that important I'd just be inclined to move those to external modules.
Did you have anything particular in mind that you could not see being doable already?