What do you think about this:
You have several different (or equal) Anker Products - and they all have the same battery pack which can be removed easily.
So the battery pack can be exchanged between the products - if the one you need at the moment is empty, you take a full one from another device and load it there ...
Of course this is only possible for products with a certain size: Robo, Speakers, and similar. But I think there are enough Anker products for such feature.