This issue of having multiple films available is exactly why I fabricated a medium format stereo camera out of a 4x5, using 2 80mm/6/3 Wide Field Ektars.  I linked the shutters with a dual air actuated shutter release (using 2 deGroeff releases) and they are pretty accurate.  I have linked the apertures to move simultaneously as well.  I had to make a stereo bellows and fit a graflok back to the camera.  If I get a chance, I'll post some photos of the camera.

 

It functions like a 4x5 field camera, not fast moving like the TL-120, but I can use all kinds of films like Pan F (for monochrome in a 6x12 roll holder), or any variety of sheet films in a Polaroid 545 with readyloads or in a Graphmatic back.  It is nice to have some 4x5 Kodak or Fuji tungsten 64 for those shots where I want a natural look under tungsten lighting.  Also, I can use this camera to shoot really great medium format macro stereo using a slide bar with the camera, exposing one side of the film at a time with the dual shutters. 

 

Sheet film stereo images are very firm and handle nicely because of the thicker film base, but the actual use of the camera in the field is slow, like when I used to shoot 8x10/11x14 view cameras. 

 

Changing film in a viewmaster?  That's why I have an extra with different film it!

 

-kp