Boiled emulsions, wow, that is an old method abandoned just about 100 years ago.
Actually, 35 mm is possible, but slitting, chopping and perfing will be complex operations as will the prevention of dust during the coating, drying and finishing process. Equipment will have to be made to help with the finishing. And, it probably will need some sort of machine to coat the lengths needed for 35mm. The thinner support is also a problem. You see, getting good subbed estar or acetate is rather difficult but glass is with us forever (or at least a long time).
MF film is made difficult by the need for thin support as well. The paper backing will be difficult to devise and this is why I have a 120 coater. I am also saving my 120 paper backing. I have a drawer full of them.