Everything you say here makes perfect sense to me. I obtained my first bees via cutouts. I was taught on videos the importance of making sure newly vacuumed bees have adequate ventilation on the trip home or they may overheat and die. The PID set us as you suggest should work for the heat side of things.
As far as the opposite is concerned; As I said earlier, you have my full attention. From what I understand, Varroa Destructor originally came from a warmer climate. Asia if I remember correctly. It may very well be that cold could be their weakness. As we know bees keep varroa plenty warm, even in the colds of the North. Mr HP what is your ideas on overcoming? Thanks.
For example; forced but controlled chill of the whole hive. No re-fridge unit needed up here. -16 degC last night.
Let say the bee can take 5-6 degC and recover just fine, we know this. But perhaps the mite dies at 10 degC. A hive chill treatment to 8 degC could potentially wipe out every mite. (Remove the queen first of course).
Also, alot of us run solid bottom boards. If mites are tossed off in grooming they can climb back up into the cluster. But what if the bottom board is cold, how cold does the bottom board have to be for the mite to be killed when dropped.
I think we have alot of advantages, and potential opportunities, in northern beekeeping. We just need some substantiated target numbers to experiment with.
Am not meaning or wanting to hijack this thread started on heat, hyperthermic treatment. I just threw the question in there in case someone browsing through knows the numbers for cold, hypothermic treatment. No intention to distract from the OP.