The problem is that it doesn't matter how genuine the need for such a pass is, if too many are issued, it's logistically impossible for them to function. It will just create two queues, one for neurotypical, able people and another for neurodivergent, disabled people. That is a mathematic certainty.
There is a solution but the theme parks will never do it because they have monetised queuing by offering ridiculously priced fast-passes for people who are rich enough or prepared to save up in order to pay the same price for a day at a theme park as you might pay for a week at Butlin's.
The solution is for theme parks to do away with queuing for everyone and offer time-slot access via an app. So at the start of the day everyone books their slots on the popular rides and turns up when they're due to ride. You miss your slot - tough luck. Ride breaks down - tough luck. But no one has to queue for longer than it takes to load one circuit of a ride.
They will never do this while people pay £1000 for a family's worth of fast passes. The answer is in the hands of the public - vote with your feet and they'll do something about it.