as others have noted, there are huge number of saddles available. And I understand that you want to have the rider on their 'best' fit saddle.
Saddle position is the foundation of a good 'fit'/posture. But you can't really make finding the perfect saddle part of what you offer. That's a huge thing by itself.
And could occupy a huge amount of your time and effort.
Sitting on a saddle for the time needed to do a fit is much less determining compared to multiple hours and days on a saddle.
You could get a representative saddle for some of the more common saddle shapes, which means maybe 8 to 10 saddles.
It's a 'chicken before/or the egg' ? conundrum.
Ride On
Yuri