I first heard about this a few years ago, adding some QD to an auto shampoo. Tried it and liked it for it contributed some lubricity/some gloss to the wash. Adding an APC would , like you say, add some oompf to the wash.
I dunno if I'd do that unless planning to reLSP anyhow. And I somehow wonder about adding a presumably high-ph product to the ONR mix. Adding QD is a completely different proposition IMO. Doesn't Optimum make a rinseless product that's more potent than ONR for just this kind of thing? I doubt that adding the APC would be a genuine equivalent to that.