This is precisely what I use. I have a 100mm f/4 Macro on another body that doesn't ever see action at the same time, so any conflict is minimal or non-existent.
My most used medium telephoto lens is the Canon FD 85mm f1.2L because I'm primarily a portrait photographer, I bought new about twenty three years ago and paid an arm and a leg for it at the time but never regretted it, but IMO the most generally useful medium telephoto prime lens is somewhere around 100mm which gives you twice the magnification of the 50mm lens and is still fairly small and easy to handle and is good for portraits as well as general outdoor photography.
Jupiter-9 85/2 (M42 mount). Fairly inexpensive when I picked it up. It's a Soviet-era Sonnar clone, so good bokeh and great for portraits. It lives on a Spotmatic at the moment.
The only issue with the J-9 is the lack of automatic aperture. Not a big deal, but many times I've thought auto aperture would be useful. Unfortunately, I shoot Pentax K and M42, and with Pentax's complete backwards-compatibility for K-mount, it seems digital shooters snap up the portrait length auto aperture lenses so they go for stupid prices now.
Here, the most used medium tele is the only one I have at the moment. A factory AI'd 180/2.8 Nikkor-P. My next longest lens is my 85/1.8 factory AI'd Nikkor. I may borrow my sister's 70-300 AF-S for use on the F5 (or on the D1H) from time to time. Probably won't use it on the F4s when that body comes, though. The lack of an aperture ring is an issue, since I usually shoot in either aperture-priority or manual mode.
Jupiter-9 85/2 (M42 mount). Fairly inexpensive when I picked it up. It's a Soviet-era Sonnar clone, so good bokeh and great for portraits. It lives on a Spotmatic at the moment.
My most used medium tele lens probably isn't considered medium at all, it's the Nikon 85 f/2. Next after that is the 200 f/4. Anything longer is impossible to shoot hand held and carrying a tripod is, for me, anathema. It's just not my style. My most used lens? It's not a long lens at all, it's the 24 mm f/2.8. I like to get in close, take the shot, and move on.