Seeing the advances of things like GravityLight, is it possible to have a power plant where people work pulling ropes for oversized verisons of GravityLight to generate 120v mains electricity? I imagine a room with a couple dozen workers and a couple hundred ropes. Each rope is connected through a pully system to a 200kg bag. Maybe a 1:8 pully ratio for the ropes, so each worker feels like they're pulling 25kg. The power plant would have a height of maybe 50 meters, which is how high the 200kg bags are raised. When one bag is brought to the top by a worker pulling the rope, they move over to another and keep pulling.
Is this a viable system? Are there any major issues that I'm missing? What effect would this have on the cost of electricity? How much would these workers be paid?