Great idea to increase the likely hood of workers going home at night but you need a bigger ( capacity ) jack for your demonstration - you have made an elegant solution to a problem but have let yourself down with a !@##$ little jack. Good job anyway.
My dad uses a 20 ton pneumatic bottle jack from princess auto for changing his sprayer tires, pretty sure he got it on sale for around $100. We only need two separate lifts (front+rear rather than all 4 corners) and move tires with pallet forks on a tractor. Works pretty slick, with 3 guys we can swap all 4 tires in about 15 minutes from start to finish pretty easily.