I have a lot of questions posed above that I'll try to answer being the 'insider' here.
If film vanishes, and we have to rely on hand made materials, then only LF format will be viable, and only speeds between ISO 1 and 100 will be viable for the immediate future after the death of an analog product. Who wants to spend hours making just one photograph? And who wants to carry a half ton of equipment into the Grand Tetons to take it? Ansel Adams work was made possible by having mass produced products. Matthew Brady was a genius, but his works are not as 'beautiful', to me they are more historical or documentary than artistic.
Photography, without silver halide will be primitive. Now, what I'm doing is not that expensive, nor am I reinventing the wheel. I know how to make the darn stuff, but I have two things against me. One is a very limited budget, and the other is getting the materials I need to do it. Correct me if I am wrong Alex, but I am pretty much there for an Azo type paper, and pretty close to having very high quality coatings.
As for the issue of having a big plant. No, you don't need one to make stuff for yourself. You can supply your needs with a quite reasonable investment as long as you make LF film and paper for either contact or enlargment.
If you talk about making quantity material, that too can be done at reasonable price, but as quantity goes up, variablility and quality goes down. Ever hear of someone getting a car that was a lemon? So, with a small coating machine, the size of a 2 car garage, I can coat 4x5, 120, and 35mm film with good quality but it will probably have dust or bubble defects here and there and it will vary in speed from batch to batch.
Lets look over the complaints here about EFKE film defects. They have a good staff with lots of knowledge but an aging plant. So, product varies from excellent to mediocre, if I read the posts right.
So, what we will see if Kodak and Fuji vanish is the gradual loss of quality color film and a deterioration of quality in B&W film as the companies equipment ages, and the staff ages. No new development will take place and products will remain frozen as is for the rest of the life of analog.
As we photo engineers die off, the chance of restarting the process becomes less and less likely. Why? There are no formulas out there. Consider the efforts to make Kodak's published AJ-12 emulsion which is supposed to have a speed of ISO 12 or so. I've used it, as a variant of it was in production in the research labs for common tests. It is indeed very fast compared to the ISO 1 or less that people observe. That is because the techniques of doing it and the fine detail are not published in the pamphlet.
Here is another item. I taught my workshops in NYC and Montana this year, and got different results at each place than I get at home. One of my students posts here. She gets slightly different results at home and has had to adjust her formula, but it works just fine. I tried her formula with several variants and it does not work for me here. So, emulsion making takes lots of understanding of technique. One of the things I taught my students, and keep corresponding with them about is refining technique and how to change the formulas to meet local conditions.
This transition is not going to be easy for any of you. Don't bury your heads in the sand until the last minute and then run around yelling about it. I'm just going to say "I told you so". Get ready now for a big bump in the road in your lifetime in analog photography.
One last item to add. If you are not ready, and can't 'roll your own' are you ready to pay the price to others to do it for you? If I sold you paper, it would be pretty expensive. After all, it is lovingly hand crafted sheet by sheet by one of the few experts in the field. (at least I can claim that)
All kidding aside, hand made products, sold on the open market will be expensive as demand will outrun supply.
PE