I hope Disney does not implement a system like this - I have never had a formal medical evaluation of my issue and I think it would be really hard to identify as sometimes I am totally fine, but other times I'm not. When I've asked doctors about it, they usually brush it off - their answer in my case might be, just don't go to theme parks. It is kind of like when you say to the doctor, when I do this, it hurts - and their response is, well don't do that!
In my day to day life, I'm not normally waiting on lines for over an hour, so I can usually manage - but theme parks are different. I've never had trouble getting
DAS at Disney after explaining my issues to them.
However, I suspect I would need to go through expensive medical testing to identify my issue, just to get a doctor's note for Universal now.
Will definitely be asking my doctor about this next time I'm there though, maybe they'll be understanding and write me a note.
I do know that all of the doctors where I live charge you to write a note. Even filling out school forms for my kids to say they have all their vaccinations - they charge $10 per page just to fill that out and the doctor doesn't even fill it out, an admin checks the computer and fills it out and then the doctor just signs it.