If I had to say a dream camera and limit it to one I'd go minimal. A Minox ML with a shutter that will last as long as a Pentax of Nikon. Small, sharp lens, a metering circuit that when used right is tack on and has a pretty good range of accessories. I loved mine and it went everywhere with me whether it was on a trip along with something like my Bronica or Leica, to the office sitting in my belt case or briefcase, a walk in the park, outside doing some cleanup or anywhere even places where I'd not carry a larger camera.
Also, as I really like the 40mm lens view, the Leica CL as a step up from the Minox. Smaller than the M mount Leica cameras with the same quality lens. Easily pocketable. A great street camera.
MF is more difficult as compromise has been my experience. I found the ETRS fits my bill in that it gives me a 6.45 image and eliminates the need for a 35mm system, just slap on the 35mm back. Saves a lot of money, allows me to know one camera and set of lenses and is a workhorse. Yes, I'd love a 6x6 but found my Rollieflexes to sit on the shelf more oft then not when grabbing something to go shooting with unless I decide purposely I want a 6x6 day.