If this is a dwelling, I am not sure why you can't use RX.
680.21(A)(1) says
Any wiring method employed shall contain an insulated copper equipment grounding conductor sized in accordance with 250.122 but not smaller than 12 AWG.
and (4) says
One-Family Dwellings. In the interior of dwelling units, or in the interior of accessory buildings associated with a dwelling unit, any of the wiring methods recognized in Chapter 3 of this Code that comply with the provisions of this section shall be permitted. Where run in a cable assembly, the equipment grounding conductor shall be permitted to be uninsulated, but it shall be enclosed within the outer sheath of the cable assembly.
Once you get to the exterior wall you will have to transition to another wiring method, RNC and THWN or whatever.
