Obviously some issues, trigger by cable release only, but that should be good enough. But what to do with a 6x9 frame? There's no way to use commercial mounts or viewers, so I guess I'd just have to cut them down.
How badly might the lenses mismatch? If they're not perfect, are they often "good enough"? I've never noticed any problems using random 35mm lenses, but maybe MF is more demanding.