What I am not sure I understand is why you don't use what is there. If I understand correctly, the studs and insulation is already in place. Therefore, what you would need to do is wire the walls as they exist now for your outlets and switches and then attach the drywall to the existing studs?
To be sure, the order is... frame the walls, install the wiring and then insulate (though in your case the wiring has to be done after the insulating) and then drywall goes on the studs. Usually before the drywall is installed, you need the building inspector to check the wiring. If there is a specific problem with you're existing studs/insulation... Let me know...