It is possible to get to CMB on RJ via AMM however I believe that the service is rather thin. Then get a flight to BKK/SIN/HKG from there and fly QF home.

The alternative solution is, as you suggested, fly to a nearby gateway in Asia like SIN or BKK, and get ur own return to CMB from either of those cities. Both cities have daily QF services from LHR and to SYD.