I have a few suggestions:
645 - Mamiya, Pentax, Bronica (all versatile, good, and cheap)
6x6 - Hasselblad, Mamiya C series TLR, Mamiya 6 (all fairly pricey except the TLR)
6x7 - Mamiya 7 (if you can afford it, this is my #1 suggestion, or the Mamiya 6 if 6x6 is fine)
6x7/6x9 multi format - Mamiya Press Universal, 2x3 Crown Graphic or 2x3 Linhof Technika (6x6 is also possible with these cameras, as is 6x4.5 vertical with the Mamiya, with the multi-format back.) The Universal is big, but not nearly as heavy as it looks (and much lighter than the Super 23). The Crown is relatively small and light, but is limited to one lens with hand held use. The Technika is somewhat of a hybrid between the Universal and the Crown, and is likely the heaviest (though most versatile) of the three of them. It has quite ample movements. The Crown and the Technika can accept any lens you can mount to a board, and they can be used with the ground glass. The Technika can be used handheld using the rangefinder with a variety of lenses, if you have the proper rangefinder cams. The Universal can be hand held with any of its lenses, though you need accessory viewfinders for the wide ones. I consider the ground glass back a most invaluable accessory for the Mamiya Press series of cameras.
I would personally have no problem hiking long distances with an RB/RZ, though they are big and relatively heavy cameras. I would opt to leave these ones behind for space considerations on longer (multiple day) hikes, but would have no problems hauling one for a one-or-two-day outing. I am a fairly healthy and athletic person, however, and I am also used to being a pack mule.
Hasselblads have the advantage of being quite compact, plus most of the advantages of an RB/RZ (high-quality component/system camera).
I have an RZ, a Universal (and a Super 23), 4x5 Linhof Technikas, 4x5 Speed Graphic, Mamiya M645, and Mamiya C-series TLR kit. I usually opt to bring the two-body, three lens Mamiya 645 kit (along with a 35mm kit) when hiking, though I have brought all of these except for the Speed. The Universal is really a great option...I just don't have as many lenses and backs for it as I would like. If I had a Mamiya 6 or 7, I would certainly bring them quite a bit...maybe even all the time.
P.S. I forgot to mention Horseman 2x3 technical cameras. They are basically like the Linhof.