So, doing exercise using the machines currently displayed at the gym seems like it would be really boring.
However, while contemplating my enormous, 50mm steel ball bearing ball, it occurred to me that if the flippers were manually operated by buttons on the floor you could stomp on, or arm-operated
levers - with a direct mechanical linkage to the paddle - you could spend an enjoyable half hour exercising while trying to get a high-score on an exercise pinball machine.
No gym subscription necessary - as you get fitter and/or more skilled, you just need to put coins in less often.
(n.b. a google-search suggests these exist, but not exactly as I envisage, with an enormous heavy ball. Most hits don't seem applicable, but there is one with foot-paddles which is something of an approximation.)