A big issue is most handheld devices are already packed to the brim with battery filling most of the space left over after the electronics are laid out so there

A big issue is most handheld devices are already packed to the brim with battery filling most of the space left over after the electronics are laid out so there's no space left for meaningful active cooling. There was a teardown of a Red camera on Linus techtips to add watercooling and the contortions required to pack everything in with the cooling was amazing.