We need to progress past triple A's I think, and establish a slightly better, at least bigger capacity battery. I've used 18650s for a lot of things, and they function decently well for most things. Aren't as common as your double A's, and triple A's though. However, they aren't some specialised hardware, and can be picked up relatively cheaply, and easily from a variety of places.

It's really the only standard that should exist. I'm pretty sure that Europe recently passed a law that Apple has to convert to USB-C before a specific date, and that would also apply to any other manufacturers that want to sell their product in Europe. USB-A, and mini USB ships have definitely sailed, but as soon as hardware wallets start bringing in their own special cables, they'll lose customers.

Everyone has a USB-C lying around at this point, and they allow decent data transfer, and charging speeds. So, they should be the standard.