Anyone who owns a bicycle can use the Asus Oxiis E250G1 Intelligent Bike Booster to transform it into an e-bike in just a few simple steps. Equipped with a cadence sensor, it is designed to respond just as quickly as a conventional e-bike, and can be charged via a USB-C charger.
Easy removability could make something like this viable. If you could just take the motor off and charge it inside, it would solve some security concerns along with the logistics.
These types of devices get an automatic pass from me: I’d rather just have a powered hub wheel that can be swapped in, a normal bike with good gearing, or a dedicated e-bike. I usually just stick with a regular bicycle but I do love my Portola too.