Passengers who have to be taken to the plane in a wheelchair can't use stairs, here in New Zealand some airports have special lifters that can fit a wheelchair that then lifts them up to the aircraft door. These are only used for regional aircraft or aircraft at remote stands which don't use a jetway. Other airports have ramps that lead up to the aircraft door and all passengers disembark on it.
It would be nice to have to invest in these types of equipment for our aircraft, you would have to consider passenger comfort and turn around times when buying this equipment.
Here is a picture of the lifter
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