Or in that case, buy a MF camera and not deal with the bulk. I still fail to see a winning case for using a LF camera for 120 film.
I use the 6x7 rollfilm back on 4x5 all the time. I've even used it on a 4x5 reducing back on a Deardorff V8, allowing me to use long lenses that will not mount on the Linhof.
If you want movements on 120, a 4x5 camera and lenses which have a 4x5 image circle can be very useful.