DKC645BLS
This one has a CO2 tank holder on the back and a hole through for a 5/8" OD hose. You could fit a Nitro tank w/ a regulator inside but it would be a tight fit. I don't think you could get 3 cornies and two gas tanks with regs in there. I've got one regulator on the outside with a hose running inside to a three way manifold. Mine has been good so far with a three tap T-Tower made out of schedule 40 3" PVC with the copper tower cooling method.
Why do you want the CO2 inside? It is very easy to get to the tank and regulator with them mounted on the back--this is how the kegerator came from the store.