I'm not familiar enough with the Fuso's bracketry to know whether this would work, but we have had, for a year or so, an aftermarket option to get a low profile air seat into a sprinter. Only 3" of vertical travel, but I've sat in them and they feel pretty good.
Sprinters mount their front seats on box-like metal seat supports, so the mounting surface is flat, so these seats are on a flat mounting plate . . . don't know if that's good for a Fuso or not.
http://sprinterstore.com/suspension_seat.htm
It doesn't look that "low profile" in the picture, but as most know, that's the way of air seats; it'll sink a lot with weight on it. Someone at the Sprinter Store can undoubtedly get you a "laden" seat height measurement.