J.S.
Your ball sounds fun !
As for 'special needs', whoa, that's pretty vague ;-)
There is no one 'thing' that's good for all children with special needs, or even all children with autism.
Some children are sensory-seeking and some children are sensory-avoiding. What could be pleasing and relaxing to one child could be a nightmare to the next one, know what I mean?
If you're interested in starting a business, could you set up a website that takes special orders? You could show sample pictures of the balls you make, and then allow parents to choose from several different sensory items on the balls. The soft side of velcro and the prickly side of velcro is something that might appeal to sensory-seeking kids. Quilted fabrics with the bumps and the 'valleys' would work well. Could you fill the ball with different stuffings? Very lightweight fluff all the way up to weighted with sand, or similar?