[wongarsu]

You can just do the equivalent of a blue-green deployment: you have two copies of the firmware, a flag that tells you which is active, and a tiny bootloader that respects that flag on startup. At any point during regular operation the firmware can update the other copy, and once done toggle the flag. Next time the scooter is started it uses the new version. If the device is shut down during update it continues to boot from the old version, and just tries again next time. Bonus points if you have a small watchdog that toggles the flag if the current version fails to boot.