Not sure how would work for powerbanks?
If say for speakers, surely the currente method is as good as carrying g precharged battery packs you swap.... Which is basically what a powerbank is? But.... Instead of charging, it would be click clunk click, and away you go, instantly fully charged again, Instead of waiting..... Maybe could work. Also maybe decided if you want to use a larger single unit and not need to swap but cope with heavier weight or 2 smaller units but still same weight but devided and interfeers with play....... I get that.
Seems like it could work. As per your example of tools, you decide on the power rating of the batteries.... Power n duration Vs weight n cost.
Could save money buying BODY ONLY UNITS (no battery, charger lead etc included).