I have a list! But I will try and make it brief.
I only have a few hives, I couldn't afford any loss whilst trying to select for a more resistant/hygienic strain.
Unless I kept buying in new resistant/hygienic queens, my attempts to select (and then maintain any strain) would be dependent on the gene pool of the drones of the surrounding area.
As I said originally, no thirst or desire for treatment free to happen around here, just flinching, so I would be back to square one in just a few seasons (just one if my swarm prevention fails!).