Hey Grouse - you really don't have to change the existing threads. You can run a sleeve into the existing threads with the new design installed into the sleeve which could have a real QD design?!? The actual BP could be nothing more than a tube that slips into the sleeve with a quick removing locking device.
You would just need some way to "lock" the sleeve in place.
It seems with this design, the BP could be quickly switched out for loose, pellets, or BH209.