Good points.
My goal is to get something back because the AA.com reservation tool is completely misleading when trying to use with a OneWorld partner. Because of the phrasing of the error message, I essentially flushed $500 down the toilet. I appreciate the sentiment that it is my honeymoon and I shouldn't fret over $500, but it's money that I would much rather have spent on spoiling my new bride. Plus, the reality is that $500 is probably a much bigger deal to me than it is to you, which is fine.
I looked into your suggestion and unfortunately, MX won't issue a ticket from MSY-PXM for our dates, even with multiple connections.
Ideally, we would like the separate MX reservation merged with our AA flights and the cost of the tickets refunded. Realizing this is unlikely, I am curious as to whether the board thinks AA might do anything to rectify the situation.