I understand that the issue with using an external spool with the AMS isnt possible because theres nothing to keep swapping the external filament in and out. so, what if we had an external stand alone extruder that did the loading and unloading. The bambu could just read it as a 2nd ams that only has a single filament. To get around needing a filament ditector for the external spool, you just let us tune the deretract distance so that it clears the Y coupler.
For bonus points, make that extruder a belt extruder and place it in a single roll filament dryer housing. Call it an Ams Flex. Set the firmware to start the print head extruder without waiting for the filament ditector to be hit. For the tpu loading portion.
This will also buy some time and create sales while you work on medium sized next gen printers. If you only release a large expensive printer, alot of feelers will be hurt. Would be nice to also extend the usability of existing printers at the same time.