SV Tech company that I work for uses a cap system. Cap splits the different between full fare economy and biz for the some trailing time period. You bank $0.50 for each $1 under cap, which can be used to go over cap on future travel (flights and/or hotels). You can fly whatever class you can get under cap, and can use banked credits with some discretion to go over cap. I've been pretty judicious with using banked credits but still managed to travel in biz a bit less than 50% of the time, PE the rest of the time.