While the MIA connection is not doable in a day, the route is possible on BA 2157 with a single stop at ANU. It's worth a call to see if there is availability and whether AA might do it for you. Bear in mind that AA has no obligation to do so. Thus, this is an ask rather than a demand.
As to covering costs in MIA. Not a chance. AA simply doesn't do it and would much prefer to cancel for a refund before laying out this type of cash expenditure.