You buy whatever lens you want, and can afford. Is your goal to only ever shoot with a 200 mm lens?

On a medium format camera, none of your current lenses would work, and you would have to buy lenses that can cover that sensor. It will likely be very expensive. If you go down the medium format road, you will need deep, deep pockets. 

If you want the same field of view as a 200 mm lens on your APS-C, you would use a 300 mm lens on a full-frame camera.

Your current 200 mm lens will still be a 200 mm lens on a full-frame, if it is a full-frame lens. If you have a lens that is made for APS-C only, it will not work on a full-frame camera. If you can put it on at all, you will get heavy vignetting as it can't cover the whole sensor.

If it is a full-frame lens, it will work just fine on your new camera, but you will see more of the world from the same distance (true 200 mm, instead of cropped to look like 300 mm).

Furthermore, there are different sizes of medium format sensors, so you have to specify a camera before you can know what lens will give you the same field of view as a 200 mm on an APS-C. But it will be more than 300 mm, that's for sure. Probably closer to 400 mm, maybe something like this: https://www.bhphotovideo.com/c/product/1045490-REG/pentax_26555_400mm_f_5_6_smc_fa_645.html

I would read up a bit more on how lenses and sensor sizes work if I were you, before shelling out the $$$.

But like I said, for the same field of view (things you see in the image) at the same distance:

300 mm on a full-frame or 400 mm on a medium format (these are not exact numbers, it depends on the camera).

The depth of field will be shallower at the same aperture (blurrier background).

Or you could just use the 200 mm lens on a full-frame and move closer, but of course the perspective would change.

85-200 mm lenses are often used for portraits on full-frame cameras.

There is no legal precedence for which lens you must use, and very few governments stipulate specific requirements when it comes to lens choices.

you said: "You can get the same image with 85mm F1.4 - F2.8 lens on a full frame camera. You only need to get closer. "

the problem I have is that I see too much of the background that I don't want to see when I use the smaller mm lens, objects to the far left and far right behind the subject.

based on the advice of people in this forum, I may just stick with my APS-C and switch to a prime lens.