Edmunds has beamsplitters that are 50/50 and ones that are 65/35. So my thinking, without having done all the research, is that you can maybe take care of the filter factors in the camera by how much light goes to each plate.
As far as using roll film is concerned, I suspect that you would have to cut the frames apart for registration anyway. So I was thinking that plain old film holders would be easier with sheet film. I have some 2.25x3.25 film holders that I got for my Baby Graphics 2x3.