Hi folks - ran a search and came up empty. Does AA allow adding an international (rather than domestic) positioning segment to a partner award, such that I pay only the difference in award fare?

I’m trying to book two tickets from JFK-MLE. I found two BA tickets in business class from LHR to MLE at 42.5K miles + $630. Right now, there’s no business class space from JFK to LHR that would connect to the LHR-MLE segment. Instead of booking a mixed-class award flight right now, can I book the LHR-MLE tickets now as partner awards, and then add the positioning JFK-LHR segment later (whether business or premium or economy)? If I can do that, will it reprice as though I booked JFK-MLE (70K miles + tax), so I only pay the difference?

I’d like to do it this way to have maximum flexibility on the positioning segment, as space opens up (or not).

Thanks!