Actually there should be no need. If you are BA gold you can call up AA reservations on the phone and read them the flight numbers and purchase the itinerary that way. As a OW Emerald you are exempt from the phone ticketing charge.

In reference to your other question, yes you will have access to MCE no matter who you book the ticket with. Just make sure that you get the AA PNR # and do the adjustments to the seats on AA.com (the reservation systems get a little "picky" when crossing airline boundaries).