> the whole operation is just not feasible in terms of cost vs. benefit.
Batteries and a motor are a huge benefit. Even if you can't squeeze in a full blown motor or 1kwh of battery, just getting an additional 200 or 300 kwh of assist in can make a huge difference.
As for cost, these guys are already doing crazy things like blood doping just to get a tiny edge.
By contrast, blood doping is much easier to get away with. Claim you had an altitude camp, inhaled CO or whatever, but you carry your blood with you.
A small motor had to fit in the tubes, somehow connect to a control, have to be integrated into the gearing which are constantly under about 300 W of torque and can be easily discovered via X-ray or maybe heat gun. That's a lot more risk vs. a much smaller reward since your laptop sized battery is likely less juice than a single energy gel.