Trying to edit a Model Type produces a RSOD

Summary: Pretty much as it says. If you go to a Model Property, then click through to its Type (which is system-generated), and then try to edit that, it goes kaboom.

Not clear how this should work. Possibly the Type should be elided altogether, and the Property should point directly through to the Model in the UI? Is there anything useful the user can do with the actual Type? It's basically an implementation detail...