Oddly enough, AA knows how long it takes to transfer baggage from one aircraft to another at the airports they service. Part of the reasoning in the connection times they make is this baggage transfer. If baggage routinely failed to make this connection, it is very likely that they would increase the MCT for this airport.

Even taking into your learned position on how huge the AA concourse is at ORD, I'd venture to say that the operations people there have a better idea of what will (in general) work,and what won't. With that said, I think it's unlikely that they would let you put the bags on an earlier flight because you think the airport is too big for them to get their job done.

Cheers.