It's not easily swap-able for chip upgrades. This assumes an upgraded chip is pin- and signal-compatible, which is almost universally incorrect.

if you've got the skill to modify the USB stick for external power without wrecking anything, it can be done with the stick as-is. This idea has been presented I don't know how many times in the seven years I've been building high-performance stick miners and it gets dismissed every time. It will continue to be dismissed every time. If you want external power, you no longer want a stick miner.