If you really want the 100% EQMs, call CO after AMEX books the ticket and buy up to the cheapest fare that gets you the 100% EQMs. People have reported that CO in many cases does not try and nick you for the change fee, and perhaps if you make the call within the 24-hour cancellation window they will almost always do it gratis.

I'm sure that there are folks here who have experience doing this...