Overall, we are saying the same thing -- that all people, whether "typical" or "disabled" -- have strengths and challenges, which need not be quantified, and which do not detract from personal worth. All people ultimately have infinite potential, and can be treasured for their individuality. Yes! I totally agree!
But I think that this part is misguided:
If most of us had one arm and were not neurologically wired to do math, the world would have developed to favor those characteristics.
I would say that most people think of themselves as "not wired to do math". As a math teacher, this math-phobia is a constant struggle for me in my work with students of all ages (and their parents!). Does this mean that we do not see mathematicians as having extra potential in this area? People do not not have the ability to fly, and we fantasize about superheroes with this ability! If a person were born with this ability, would it not be universally recognized as added potential?
Also, if in fact no potential was lost with disabilities, then why would we bother with medical, therapeutic, and technological measures to restore it? I am extremely nearsighted. If glasses had not been invented, I would be functionally blind, and my potential would definitely be diminished. I could not drive or do most sports, participation in an ordinary classroom would be nearly impossible, and even ordinary tasks would be challenging. With glasses, I am considered able-bodied. One of the things that I find so exciting about T21 is that progress has been so rapid in the restoration of lost potential that we have no idea of how much further we will be able to go. This is a good thing!
I also believe that this is not limited to people with "disabilities". As we agreed earlier, all people have strengths and weaknesses. The struggle around how much to put into "normalizing" the child comes from the same parental headspace as how much to push a child into sports, music lessons, extra enrichment etc. vs. "letting them just be kids". To what extent do we try to "maximize our children's potential" vs. celebrating them "just the way they are"?
Getting back to those balloons. I think that what these "potential balloons" really represent is a combination of our abilities and our self-image. As parents, we try to inflate our children's balloons as much as we can without popping them. We want our children to have the greatest potential they can. As adults, we can sometimes continue inflating our balloons. Usually though, we go in a particular direction and hit the latex. This may or may not be related to a "disability", but it is always a struggle.
In general, when faced with an area of struggle, we have three choices. We can look for ways to overcome the difficulty, either alone or with education/medicine/technology. We can accept our level of performance in that area and focus on other areas where we have strengths. Or we can redefine our standard to whatever our level is and try to get society to accept our definition. All three of these strategies have their place! There are definitely areas where society's definitions impose limits which deserve to be shattered, and doing so will improve society. But the first two are the means to improving ourselves.