Maybe. Specially with single battery mods with slower charging and the only way to get going again is to be prepared with some fresh ones. My guess is that a good 2x ~3000mAH will last most people a few days and almost everyone at least a day. USB chargers are everywhere already, and with a charge rate of ~1A, it shouldn't take much time to get operable even from a depleted pack. With a bit of engineering (we gotta do something, right?), we can avoid the unnecessary complexity of being bound to special external chargers and continuously opening/closing your vape + mechanical contact stresses, battery sleeve wear and tear.. If we're looking for a minimal complexity circuit, we can try think up some under-voltage + fuse circuit, like some zener + mosfet + polyfuse set up.. imho this should be part of a bare minimum DIY scheme if not using a BMS.