I've been thinking of that since I got my Kiev. When I started back in photography, I thought I was the man when I got my 28mm and 135mm. But I still often had to do a lot of moving around to get the framing I wanted. And for the most part that worked. Then I got other lenses. Some, like the 18mm I really did need at times. The 300mm, 80-200mm, and the other zooms were fun I thought, but sure heavy. I didn't have to move so much. I have decided that either with the Kiev, or the ST 801/901, I want to try using less lenses, and certainly not zoom even with the SLRs. Don't know what I will look for with the Kiev, but with the SLRs it will probably be 135, 28, 18, and of course, the 50. It should be interesting.
With the Kiev, I suppose a 135 and hopefully something wider that 35mm. I have used that equivalent in 6x7, but only because at one time that was all the wide I had. I just prefer wider. I have tried it with SLR and just don't care for it. Not wide enough for my tastes.