The OP's suggestion to put a digital camera in a Zeiss Ikon body, really resonated with me. I've often thought that the ideal digital would have the same body as one's favorite comfortable, familiar film camera. So an M6/MP or Zeiss body sounds right. But also: How about a Nikon digital in the same body as an FA, or F3 (etc.). I would not insist on full-frame, but I would insist that the crop factor could not be more than 1.2:1. I would not be a megapixel hog, either. Eight MP is probably enough, so as to balance resolution against excellent high ISO performance. I guess a good clean 1600 would be enough. I want live view as well as a good optical finder. A rangefinder for my Leica lenses, and an SLR for my Nikon glass.
And let's keep it simple. None of your 99-point autofocus, for instance. One point will do. The lens has never been made that can focus at more than one distance at a time. And let's get some real dynamic range, OK? I'm tired of seeing those blown highlights blinking on the LCD. Built-in flash would be welcome. Maybe the ability to shoot in TIFF as well as JPEG and raw.