Tripp,
Getting back to the question that you asked (we got a little bit off track there). If you and your client still want an isolated ground circuit, you must use cable with an insulated ground wire. Unfortunately the code does not allow taping the red wire green if it is #12 AWG. If you are not getting the work inspected, I would certainly tape the red wire.
If the work is to be inspected, the first solution to that conundrum (is that really a word?) is to use 1/2" flex with two green ground conductors and a metal cut in box or metal 4" square box if in new construction. You could then put a band of yellow tape on the green isolated ground wire, leaving the green exposed to comply with the NEC.
One trick that you may have used with flex is to pre-install the conductors in the flex (somebody will probably point out that the NEC forbids this). You can then install the flex like cable and strap every 4-1/2 feet, if possible.
As previously indicated special IG cable is available, but quite expensive.
Best of luck,
Larry
