The job is being over engineered.
Tell the client that his solution is to go to a 'dedicated ground'.
Avoid any worries about IG engineering.
Go with Reno's solution.
The results will be fine.
You can still use an IG receptacle just for looks, no harm there.
Better still go to a novel color like grey with a totally conventional receptacle.
Or you can use a Decora style receptacle for this one circuit in a house that is conventional otherwise, etc.
Regular 12-2 or 14-2 Romex will do you fine.
