if they could sell a monochrome camera to people other than photography forum members, they would have done it already.

I agree and don't think the Leica has sold very well.
I mean, why would anyone want to buy a camera that has that limitation?
What limitation? What is there beside B&W? There are plenty of people that still shoot B&W. Leica doesn't sell many M cameras to start with. But since the released the M246 after the M monochrome says that it sold enough. Leica has it easy actually since they use DNG as raw. They simply output the monochrome as monochrome DNG and the S/W is already in place to handle it. If Fuji released one they would be be stuck with the F/W to support and DNG makes the most sense and that would be more work. In other words I expect it would be a much bigger impact for Fuji than Leica.
I've rented the Leica M monochrome (18 true MP) and the images are better than my Pro2 converted. First they are a true 18 MP while Fuji is probably 12 to 14 after the Xtrans processing and interpolation. Second there is no smearing of detail - no interpolation. Third the tonal gradation is richer. On top of that any S/W package handles DNG.
The difference is small and it is subtle but it is there. At some point I will have a monochrome camera. But I doubt Fuji will ever make one. There are two downsides of a digital monochrome camera. It is a digital camera so the response is linear - there is no shoulder so exposure becomes extremely critical. The second is if someone does not have experience with B&W they don't understand the necessity to under stand spectral balancing the scene which means the use of external filters. There is no color to convert from. So the attitude shown on this post would significantly limit the people interested in the camera. So I don't see Fuji going that route.
There is a monochrome street camera in my future - I just don't see it being a Fuji.
Photoshop and the Fuji film simulations will allow just about anything a person wants to do with an image.
Naturally, if someone wants to spend their money on a one-trick pony that's their business and whatever floats their boat is fine with me. :-D