35 mm film was designed to be used with a pressure plate, so it won't stay flat by itself. If you don't want to use guides for every strip, which won't allow you to expose the edges of the film, I would use a glass plate between the film and the lens, to have something to press the film against, and then a large pressure plate on the back. Of course, since the emulsion would sit on the glass, one would have to make the pressure plate list during film transport, otherwise you will likely scratch the emulsion. I'm thinking there should be also a device that lifts the film off the glass completely during transport. Also, since the 35mm cassettes are wider then the film surface, they will have to be staggered so the film strips can be flush with another. If you didn't want to waste the first 10-12 inch of film, you would also have to load the thing in the dark.