If flying is the issue and not charging in the hotel room. Until an optional second battery is available for those of us who travel with an eMtb I don't see how it would be possible to use it in 2 different regions.
However, when traveling it would be possible to drop the motor and remove the battery, on the Amflow it is a relatively straight forward process as long as you have a chain ring tool.
I have come to the realization that for my needs I am having to have a bike dedicated for each region that I ride since where I live there is no mountain biking practically speaking. It is not ideal or inexpensive but just a fact of life.
There's no mountain biking in Kona? I had heard Maui had quite a scene, and there's a lot more open land on the the big island so I figured there'd be some good stuff there.
Regarding your statements on removable batteries, bikes, and regions, I'm a little confused what you are advocating for. You wrote "Until an optional second battery is available for those of us who travel with an eMtb I don't see how it would be possible to use it in 2 different regions." and you wrote "However, when traveling it would be possible to drop the motor and remove the battery, on the Amflow it is a relatively straight forward process as long as you have a chain ring tool."
So is the problem with using your bike in 2 regions due to the airline restrictions on traveling with the battery, difficulty of removing the battery, or is it due to geofencing by the motor/battery maker? It isn't clear to me based on your description as you seem to say you would need an optional 2nd battery, but also say it is a relatively straightforward process to remove it, and the use of the term "regions" makes it sound like there is some sort of software limitation, like each battery is coded to a specific region.
Sorry if I'm being dense, but I'm hoping to do some international travel with my next bike, so these sorts of underdiscussed details may be very key in determining what bikes I consider.
FYI for those who haven't come across this option, I have seen some bike rental places in popular MTB travel destinations are also offering battery rentals, so you could fly with your own bike, leaving the battery at home, and simply rent a battery while you are in whatever cool spot you have chosen. Not sure how widespread it is yet, but hopefully it catches on.