You could sample it like this:
Record whatever # of notes you feel represents the instrument well at however many velocities you choose. In this case I would say you want a minimum of 3 or 4 velocity layers.
Import these samples into kontakt and map them. Make sure to loop them all (with crossfades so each loop doesn’t sound jagged when it repeats) so that the sound may sustain until you release a key. Then map either something like the modwheel or keyboard aftertouch to control which of the velocity layers is selected.
Kontakt has something called AET filters that lets you blend each velocity layer together with only a few samples so that the morphing won’t be abrupt and quantized sounding. iirc, you select the group of samples you all want morphed, right click, and there’s an option that lets you have kontakt automatically create this filter for you.
Perhaps there’s a more efficient way to do this, but while being away from the computer this is what comes to mind procedurally.
And are the drone notes included in the key set? Or are they separate buttons or something on the instrument? I’m not quite familiar with that mechanism but if they are separate keys you could just have one group for all the normal notes, then place the drones an octave lower or something