I have never seen or heard of an AC discount code that allows a stopover outside Canada and continuing onwards on a non-AC flight (and LH/LX/OS/etc. operated flights can only be booked under the applicable AC codeshare flight number if it's a connecting flight).

AC or any competent travel agent should have no problem booking the desired itinerary on AC ticket stock, but afaik the itinerary wouldn't work with any discount code.