If you want to maximize your one way trips on AA, you are going to want to start flying connections instead of non-stop. I think HPN-MIA will go through ORD and LGA-MIA will go through BOS or some other places.

Doing so will increase your travel time quite a good bit though.

Alternatively, you can charge everything on your AA credit cards and hope that you'll hit the 1M mark before they decide to stop the CC miles to count toward the 1M miles.

regards,
drew