I don't see the point of a built-in cut-off. So if you want to buy multiple packs each time you are paying extra for the cut-off, when you really could buy normal packs and a single external cut-off. And then what do you do if the pack dies or cut-off dies, replace both pieces even though one part is still fine? And then when you upgrade your ESC to one that has a cut-off already what happens there? Do you use the one in the lipo pack or the one in the ESC. Just doesn't seem very effective or useful in the design.