I have seen one play dr who was very into mixing age play. We both developed our med fetish during our teenage exams, and that's what we did. We were both about the same age, around 30. He strongly preferred the doctor role, but we did switch and examine each other.
To recreate the exams and keep them realistic, we would set a scene up such as me being 15 and needing a sports physical. He preferred to just have me strip my shirt off and the the rest of the exam around my clothing, as was done to both of us.
I still remember my first exam. Him wearing a white coat and me lying on the table in his hotel room as he got lower and lower on the abdominal exam. This caused a full election, just as it did at my pediatrician. He continued small talk about school in a kind of demeaning tone as he undid my short and lowered the front of my whitey tighties. He throughly examine my genitals, making comments on how well I was developing and my public hair growth. I was acting nervous, shy, and embarrassed and as I raised my head to warch, he pushed my chest back onto the table and told me to “just relax and be a good boy. The doctor needs to have a quick peek at your privates.”
We did several iterations of exams that day. Great memory. I was able to meet up with him one more time, this time as a group exam with one other guy there about our same age as well. They had done exams together once before as well, I had never met the third guy. We did multiple exams with different scenarios, bothers/friends, doctor and medical student, etc etc.
I remember the first scenario, I was the first “brother” to be examined. It was much like what I described above. Interesting feeling having the new guy get to see my genitals first and watch me get a thorough palpation, but after a few minutes the roles were reversed and I was watching him get the same treatment.
One favorite of mine from that day was me acting as a doctor teaching my medical student on the original doctor. He was lying there with his underwear around his thighs, as I demonstrated a complete genital exam and watched my med student then perform it. He was completely erect and dripping precut, and as he squirmed around and was nervous and shy, I just said “relax and be a good boy.”