If you are "locked" in on 6x7 then you have your choices narrowed a bit. I have never used a Mamiya RZ67, but I did own a very nice RB67 with three lenses for about a year and a half. For me it was only a tripod camera. Now, if you are of a large body size you might be happy strapping it around your neck, but not me. I did love the rotating back and it being 6x7, but I never got used to the separate cocking and film advance. The optics were also very, very good. I already had a Hasselblad 500C so the RB67 went up for sale. Like I said before, I have and use the Pentax 67 the most of all my cameras, but if I were to start all over and wanted a more portable and modular 6x7 there would only be one choice. That choice would be the Bronica GS-1 with the speed-power grip added. You would have everything you seem to be asking for in one much smaller package than the RZ67. I think the RB67 and RZ67 are really fine cameras, but I just don't find them that portable. If I'm going to lug something that big up a hill I'll take my 4x5 field camera with three lenses, 4 film holders and a 120 6x7 roll back and have the same weight and a much larger negative to boot.