Since ghostthokitem defaults to 1, it won't work unless you set it to 0 in an S_SKIN. So you can't really make a universal thokitem SOC that does anything different than the usual thokitem, aside from graphics.
You could always copy one of the default .plr characters as a .wad and add ghosthokitem = 0 to the S_SKIN. Add the copy wad, switch to the copy skin, and then the SOC should work as long as nothing else is broken.