Well, if you keep leather conditioned, it should be fine. Plus with a solo sprung seat, you can always put on a cover to protect it...
I'm curious never having had a solo seat as to comfort level. The old style had individually sprung seats, with all the support carried by a dozen or so transverse springs, then the whole seat suspended on more springs.
Done right, I think it would be a lot more comfortable than a hard steel pan with an inch or two of foam - any kind of foam. The pans are just much cheaper to make.
Plus the sprung seats would age to fit your butt better...
I don't know for sure, because I've never tried one.
How about sprung seat on transverse spring supports WITH a layer of gel, then covered with leather... blissssssssssssss....