With adapters, the Leica S (maybe not "real" medium format as defined by some) has to
be one of the most versatile platforms.
You can use Leicas expensive 120 macro.
I use a metabones Mamiya to Leica adapter and use an older Mamiya manual focus
120 macro with exceptional results.
With appropriate third party adapters you can use Hasselblad V and H series lenses,
Pentax 67 lenses,and all Mamiya lenses with an aperture ring.
With Leicas expensive adapters (over $2K) one can also use Contax 645 and Hasselblad H
lenses and maintain autofocus functionality if that is a need for you.
Worth considering,at least, as there can be some decent deals around for used or refurb'd
S2 camera bodies.
Mark
www.marktomalty.com