(B) Sizes 4 AWG or Larger. An insulated grounded conductor 4 AWG or larger shall be identified by one of the following means:
(1) A continuous white outer finish.
(2) A continuous gray outer finish
(3) Three continuous white stripes along its entire length on other than green insulation. See related ROP
(4) At the time of installation, by a distinctive white or gray marking at its terminations. This marking shall encircle the conductor or insulation.
I think you will get many that think you can not do what you are asking, but unless they can find some other code section that says otherwise I think you can, but would need to somehow identify it to not be a grounded conductor. If it were smaller than 4 AWG I say no way other than the permitted exceptions that would really only apply for multi-conductor assemblies like cables and cords.
The following shall be use ONLY for the grounded circuit conductor, unless otherwise permitted in 200.7(B) and (C):
(1) A conductor with continuous white or gray covering
What about 200.7(A)?
I don't see anything that limits that to specific conductors sizes.
As you noted, the exceptions deals with cable assemblies, and with less than 50V.