No fighting intended, I think it's interesting to see that there's many ways of doings things, and doing a sort of mental whiteboard exercise on what the benefits and drawbacks of different things are... Like, using cylindrical cells would let me share cells with my head lamp, swap cells, independently charge cells and keep spare charged cells ready.
While using a pouch cell keeps the profile much more slim, portable, still has opportunities for really high capacity in watt hours, and allows for a more robust case design that doesn't have the structural weakness of a battery door.
And if you put the pouch cell on a set of wires with a small pluggable connector to the main PCB (and a case that can screw open/shut) it's still an item the user can replace with 5 minutes and a screwdriver if it wears out from many cycles over a period of years.