The MD equivalent for aviation might be an
ATP/A&P who once worked as an air traffic controller and has an
aerospace
engineering degree.

I think even that is being way generous unless there is way more to
being an ATCS than to being an ATP/A&P.

I have a PhD in engineering and use it professionally. I am also and
ATP/A&P recreationally, and I think the training and skull sweat
required to get to that level in aviation doesn't even come close to
what it takes to get a BS in engineering, never mind the PhD. In fact,
I know at least one ATP/A&P who flunked out of engineering school.

When it comes to the private/instrument, I think the professional
equivalent might be something along the lines of those 3 month training
courses required to become a VCR repairman - and then only if it's done
right, rather than just meeting minimum requirements.

Michael