Not that I would do this, but, my dog would easily pass any of your service dog tests and he's only one year old.

While there's lots of abuse by people bringing obviously untrained and unqualified animals on a flight, there is just as much abuse by people who take well trained dogs on flights and simply don't want to subject them to cargo transport -- the abuse is just much less noticed for obvious reasons.

Personally, I would prefer to simply adjust the system so that any sufficiently capable dog can travel in the cabin for a fee, which would of course be waived for people with disabilities.