Maybe you can take some pics of the job? I'd really like to see how it turns out.
I was doing some heavy research, basically trying for the same result as your customer, but I wanted to be able to lock and unlock the doors with a keyless remote (no poppers) then open the door with the handle. Pretty much the same as a modern vehicle.
The spring loaded one that returns looks like it'll work, but seemed a little bit flimsy to me.
I did find an article, think it was in a magazine, where they had the same type of handle "holder" custom made. Have to see if I can find that one.
Anyway, good luck, let us know how you make out, and remember.... Pictures!