Please clarify what is a Natural Gateway?
Would MIA be allowed on a Stopover BKKx-NRTx-LAXx-MIA-LHR-LAXx-NRTx-BKK this would mean that LAX is the natural Gateway
or would it have to be BKKx-NRTx-LAXx-LHR-MIA-LAXx-NRTx-BKK in which case perhaps MIA could be accepted as the Natural Gateway