The problem stems from people basically wanting "free energy" and I'm not talking about a conspiracy type thing, either.

Like I originally said, it would be A LOT of work (re:energy) to get the system to produce the wanted energy the OP is hoping to get out of it. Problem is, your wasting your leg power (energy) to get inefficient power to the motor. You might as well just pedal along with the motor/batteries and drop their energy consumption, thereby getting a net gain WITHOUT the inefficiency of what he's trying to accomplish.

As Jethro kinda said, why would you want to use an inefficient setup rather than a more efficient one?

If you pedaled with 300w and just used regular bicycle technology you get about 285w of power out (95% efficient).
With the bicycle "system" the OP wants, it's prolly about 40% efficient...
Why would I want to get 120w out of 300w of power?
Answer: I wouldn't!

P.S. I know there are some people out there that will say, "Well if the tour de france" people can pedal with about 500w of power and get speeds of 40mph.."

Here's the thing..
Their bicycles weigh about 12lbs! 120psi, 1" tires and Lycra / aerodynamic riding plays a HUGE role.