You should be able to check bags through even if it is two PNRs. I can't see IIROPs being that different either. If you have any sort of status, baggage allowance shouldn't matter. If this were me, I book two tickets. But, I have status.
Are you sure they will through-check bags? What about this change in policy earlier in the year?
https://www.flyertalk.com/forum/amer...aa-policy.html