It's an fascinating topic and whilst I think it sounds interesting I question how open MTBers would be to some changes.
As mentioned previously, the main adjustments made to a road bike fit are with the seatpost, saddle, bars and stem (and crank length). All those things are more difficult on an MTB.
Your seatpost will be a dropper so you can't change it for another with different set-back. Saddle could be changed, but you don't have much room for movement there.
Bars is doable, though a lot of MTBers have some strong views on width already, you could look at rise and sweep though. Stems really affect handling so suggesting someone put a 90mm stem on instead of their current 35mm may not be well received.
This is also ignoring that most fitting is done on a static bike, with an MTB suspension sag alone will have some impact too.
So my belief is that bike fitting is all about a rider learning what they are feeling.
*applause*
More of this and less of the fit formulas is what bike fitting needs.
BUT, most people don’t really seem to care. Being uncomfortable is “normal” on a bike, so they just accept it.
I'm perfectly comfy on all my bikes. All are set up very unconventionally to give that comfort. too much of "bike fit" is subjective IMO and also based around fashion
OP you at least seem to understand the issue. MTBs aren’t very adjustable in terms of fit.
However in think there is a market helping people get things right. A fleet of hire demo bikes would be great but expensive. Could people try the fit on a hardtail if they normally ride FS? That would save a heap of money
Loan or rental of kit would be great for example bars
suspension set up would be the first thing I’d pay for
I do wonder if you kind of need a day package. 2 hours coaching. Discussion and adjustment session. 2 hours coaching type thing
Oh and gravel fit might be an easie place to start. More adjustable and potentially huge market. This will be a service people pay for as they change bikes
