Yeah. AA batteries suck though! I’d be happy if they used 14500 cells or something. but the form factor was probably the issue, the controller is a chonk in the middle already with the flat battery pack

18650 is awesome, a good balance of weight to capacity. They are the standard cells used in laptops, vapes, small powerbanks, power tool batteries, and so on. They can also go into a fairly standard charger for AA and AAA batteries and give a lovely nominal 3.7V.

That said, pouches are better for inside a device like a controller. The weight of a battery is significantly influenced by the casing. A pouch is almost entirely capacity, a cell like an 18650 or AA is largely the metal of the casing. If you have the pouch inside the plastic of the device you can save that weight.