The attractiveness of Sanwa buttons is the very little deadzone involved in pushing the button combined with the soft feel and short throw. The wide flat surface of the button is also preferred by fighting game players to the concave shaped buttons.
The potential market would be those players who have older custom arcade sticks, like a MAS stick, or those who have American style cabinets who would like to replace their buttons with Sanwas, but do not want to go through the effort involved in drilling the holes out and routing the bottom of their panel.
These players are not all fighting gamers either. In recent years a small community of players who are fans of candy cabs and Japanese arcade games has emerged. Most of these players want a candy cab, but they are not very common or available, and they have settled for an American style cab. I am one of them. They would welcome a button that is functionally very similar to an OBSF.
I personally would be putting these into my MAS stick, my cab, and my custom joystick. This combined with a Seimitsu LS-56 + Bat top would give a Japanese feel, but would preserve the case and the ability to switch back to American parts.
I don't think you would make any money on this. Maybe if you charged $5 a button you would, but I'm not sure people would be willing to buy at that price. OBSF's used to sell around that though, so you never know. But for 7k that would mean you would have to sell 1400 buttons to break even, and I don't think there would be even half of that many people interested.
But if you could make a button that was once cheaper and better than Sanwas, then I think you would find a goldmine. Sanwa buttons always seemed overpriced and less durable to me, even though their performance was great.
It's just one of those fanciful things. There are a dozen more out there that I think about occasionally.
An ArcadeVGA like graphics card that supports native arcade resolution output over composite, S-video, and component video would be another thing I have always wanted. This one is probably more possible, but has yet to see any development.