I use two 5x7 Durst 138S for all formats. One is setup with a variable contrast head for black and white and the other has a color head that is used for color. The color one can only handle 4x5 film however. I don't find it a big deal to swap the lenses to go from one format to another. I used to use two Omega D5s in the same type of setup before I decided I needed a 5x7 camera.

I do wish I had more negative carriers for the Durst. That's the one thing I don't like swapping formats in.