Use ITA Matrix and then ITA-Matrix-Powertools (
ITA-Matrix-PowerTools - Userscript for Orbitz/DL/UA/AA/BA/CZ/IB/LA/LH/LX/TK )... it will find a way to let you book via aa.com, though it may be the Amadeus version of AA. I've booked a few more complex itineraries in this manner.