I'm wondering if the energy loss through the tensioning and/or internal gears is at all significant. Instead, would it make sense to have a heavy flywheel, a f

I'm wondering if the energy loss through the tensioning and/or internal gears is at all significant. Instead, would it make sense to have a heavy flywheel, a fixie gear, and a way to slowly ramp up the power draw, so the power draw itself is the "gear" that allows you to go from a hard-to-start heavy wheel to a smoothly-running wheel?