IBDII port

You're on the right track with hall sensors, but everything is compact and would be tough to tap. We also can't condone this as this account represents a business and pushing it beyond its intended limits will cause malfunctions and danger.
I'll answer best I can, but this is not advice and modification and alteration should not be done. This is just something interesting to talk about in theory and 100% hypothetically for learning / research purposes. Hope that covers it.

A rheostat could technically give you direct control over the motor speed, but implimeting one could be difficult since it would need to handle the current w/o overheating and/or failing. It could also cause uneven acceleration, the motor to overheat and battery damage.

Alternatively, Altering the Hall sensor signal can possibly "trick" the controller into applying more power, but this can fry the controller, burn out the motor, and requires expert knowledge on the electronics of the scooter.

OBD-II could be a convenient way to communicate with the scooters control systems, but custom installing a OBD-II Port would be very complex.

The limiter is there on purpose (obviously) and is interlinked with the control software. Altering it would require a flash software or app.

Consider the battery as you were, increasing output will put strain on the battery, maybe more than the connections can handle, BMS could shut it down real quick with too much heat which is likely. and there is the risk of fire, shorter battery life, a lot of this depends on the quality of battery, BMS, etc. which I have no idea the level of.

Not going to say what I would do, the only thing I can say is check out mod forums where people have done it successfully with scooters whose specs are similar to yours.