1. The bottom pump would still have to pressurize the water up to a small amount in order to prevent a vacuum at the surface.
15PSI = ~30 feet. This means that for each 30 feet that the water has to be lifted the pump has to create an extra 15PSI.
pumping the water back down the well does not help more than 30 feet since if the water table is lower than 30 feet you would be pulling a vacuum at the surface.
2. Check your local codes. Pumping water back down a well is not allowed in some areas. (here in MN for example does not allow it)
I feel that open loop is a good stepping stone, however it's not a destination. The goal should be to plan for closed loop.
Personally I'm going to try and drill a 3/4 well down 60 feet this summer and the thought is that I can cap the bottom end and slide a pipe inside the pipe to create a closed loop well. I'll need 12 of them in parallel, however the idea is to reduce the drilling costs by eliminating the need for a large rig or drilling mud.