Using AC and CO and MX I have done YYC-YYZ-IAH-CUN-MER-IAH-YYZ-YYC with stopover privileges in IAH and YYZ for 1/3 the fare of YYC-IAH or YYC-YYZ. I know this example doesn't help to get you away from AC but it does show what creativity can yield in terms of lower price, with full flexibility and a built in vacation for your business trip.