You mean something like the pictures attached?
This sort of stuff should be relatively easy with the modular standard that I'll be proposing - provided that a certain amount of units would need to be produced and sold.
I haven't found a decent Mod wheel part yet. I have the Doepfer part here - forgive me for saying that it is of low build quality. So that would have to be developed as well. Not a problem on its own, but enough of them will have to be produced to make it affordable. Crowdfunding could do the trick.
The build-in depth of a part like this will require the enclosure to be at least 45 mm high, making a desktop box rather bulky - some people took issue with this. None of that is an issue when you flush mount the modules on Eurorack rails - as long as there's enough room under your desktop.