Great, I guess we'll have to gate ADA compliance on overhauling the entire US healthcare system, first. Heaven forbid someone has to do work in the same environment as a blind person with a service animal.

Until we do, are there any other forms of work that you feel that an employee/contractor/etc. should be able to shirk by claiming that they have a medical condition, without providing a shred of evidence thereof?

A medical note for a chronic, life-threatening condition is a sufficient, and reasonable requirement, and is good from years to decades.