This is an easy one. I would replace all those swing checks with spring loaded ones. Then cut out the tee with the pressure switches sticking up, and place a 2” CSV in that spot. Come off the main manifold, like where the ball valve sticks out to the left, to attach an 80 gallon size bladder tank. Mount all three pressure switches on a tee as close to the pressure tank as possible. Stagger the pressure settings 5 or 10 PSI apart, and let it run.
Example pressure setting;
Pump #1
On at 60
Off at 70
CSV at 60
Pump #2
On at 50
Off at 60
CSV at 50
Pump #3
On at 40
Off at 50
CSV at 40
Something like this
http://cyclestopvalves.com/smf/index.php?topic=111.0