Book separate tickets online in the desired inventory (First w or w/o restrictions etc) and then call AA and have the PNRs linked together.
Obviously need to make certain that the connection times are legal .. etc...
I used an 'I' fare (Discount Business) transpond MSP-ORD-LHR. When I tried booking Discount Business with Restrictions on MSP-ORD-LHR-AMS the fare jumped over $1500. I booked the LHR-AMS as a $90 return ticket instead as a separate reservation (on aa.com) and then called AA to link them together.
Worked great... all using aa.com.
Does this help???