I know guys that are dual typed at a 135, not only do you have to be proficient, but you have the check rides to prove it.

As far as myself, at any moment I'd feel safe and fine flying any of the tbm models, merdians, mirage/matrix, sr-22, pa32, c310, and a few others. Literally just hop in and go comfortable. I don't see how it would be q problem to be safe to only be limited to only two airframes. Your bonus would be that they would be the exact same planes each time.