Many of the RB lenses were duplicated in RZ, for reasons mentioned above. There is nothing illogical about it - it is a natural evolution to accommodate AE metering etc on the RZ.
I do not own the RZ 75 Shift, but I do own the 50 Shift for Mamiya 645. If they are similar, the barrel will rotate 90 deg either side of horizontal.
A tilt capability would certainly be a great addition, though. I have seen kludged solutions for other mounts, and then there may also be Hartblei or other possibilities in native RZ mount, although I haven't done much searching. A friend of mine uses a Zorki or something on his Hassy. He had it transformed to Hasselblad mount, from I dunno which original mount. So something similar could be possible with RZ 67, but how you will incorporate the electronics for the leaf shutter is another matter. His photographs are really terrific, so it was worth the effort for him.