I like the Autochrome Lumière photos from 100 years ago very much! I understand it was made with potato starch, but no one has reproduced it successfully yet.
Trying to reproduce this effect, shouldn't it also be possible to coat three blank film sheets and expose each with a different color filter (at the same scene)? Then combine the three negatives and make one print?
This is in fact in theory the same as what we still do making three digital negatives (digital color separation) for color gum printing nowadays.
I once bought three old 4x5" wooden film holders with each a different glass plate in it: red, green and blue (if I'm right, would have to check). I suppose they where used for a process like this?
(BTW: I like your motivation/attitude towards experimental photography)