Make PIP Assessment Centres more easily accessible for people who are ill

My nephew has Asperger's Syndrome. He has been unable to claim PIP because he cannot "hold on" to the phone to speak to an operator, have the right documents at the time he makes the call, completely understand the telephone conversation, understand how to fill in the form to explain his situation or attend the assessment centre, as this would involve interacting with people and travelling to an unknown place. I cannot start the claim proccess for him by phone, as he has to be present and I do not live near him.