I would like to suggest a feature. The feature is called Battery Super Saving Mode. This feature is available to other ROM (Flyme OS). Once enabled the OS will only allow some apps like phone and messaging to extend the battery life of the phone. In this mode by default only allows phone and messaging app however it can still allow apps. I attached the screenshot of the said feature in the Flyme OS phone.
This will be really useful for a user that so far away from charging station or does not have a power bank and the phone battery is 10% or below.