Oh, I forgot frame prep tools, though it is a wash among methods.

Problem with frame building is that the moment you come up with a great idea, there is someone to tell you that you can't get there from here. Fillet brazing stainless is a problem, which is probably why you are encountering resistance. The good news is that it is pretty easy to do with silver. Personally I would have no problem doing my own bike that way, and it used to be pretty common to do it that way. The prevailing view today is that it is not safe, which means that if anything ever goes wrong you are not going to have any cover.

Filler and flux master Freddy Parr, if he is still making stuff, had a miracle material that I believe brazes silver and is easy to use. I don't know about current availability. You could google around. However, in my mind it is an unproven material, that while I would not really hesitate to use it, I am not sure what the basis is for assuming a lessor failure rate than Silver that has just been out there a lot longer. Whether one should base a business model around a single boutique product that does not have a long term record, and has has supply problems is a question I would want to look into.

Again, it is kinda a twinkie idea for a business. A lot of stainless and Ti bikes get some paint, don't they? For decals, a unified look, and stuff like pinstripes. It just becomes one more thing a competitor is offering to professionalize his offerings, and make them more distinct. I think that avoiding paint, as massively appealing as it is, is sorta solving a problem most people did not even know they had, while frame making has lots of real problems to solve for people, that you can solve in steel. These would be fit, purpose, quality, and looks. Plus personalizing the sales process so that people feel their needs are being met at the level they have come to expect in other parts of their lives.

I always say to newbies that they should look at how Bike Friday does it. Not that you want to make folding bikes. But they have come up with a method of providing well regarded results with the cheapest of materials and methods. They do TIG, but that's a production thing in their case, they also braze. These days we also have ex-BF dude Rob English. Check out his site. He makes interesting custom bikes carrying over the extreme cheapness approach of BF. He does some extreme things, but simply, he just brass brazes. Also, while I have no idea how he is doing, his stuff looks more likely than some to attract a full build than just a frame sale, which is one key to more profit per frame sale. The bikes he builds are ones most people would want him to outfit, which is clever.

There are any number of other makers one could point to. I just chose BF, and RE, because they have methods that choose the cheapest means to achieve the highest value add. Lets say a person did do Ti to save clients the need to buy a bottle of touch-up paint (and I realize there are deeper problems than that), that is a massive upfront cost to provide a benefit most people will not add too many dollars to a sticker price in order to get. Even the ride differences are pretty difficult to spot in a blind test kind of setting. Your job is to maximize your profit margin while providing clients with the sense of the greatest value increase that they can have. Sadly for the metal guys, paint is a lot of that perceived value. I can think of a number of very revered makers whose bikes I would never look at if they used a different painter. Sadly good paint is expensive and kinda nixes the idea of getting a nice looking ride into someone's hands cheaply. One option is to do steel and find a local powder coater you can work with. That will handle the purely functional bikes.