FUJI GX680!!!!!! Let me live vicariously through you!
Seriously, though. In your case it might actually make sense. It's definitely going to be a pain like RB67 (probably an even bigger pain, actually), but if you're interested in large format the GX680 has some useful movements. I mean, if you're even thinking 4x5 you should just put asaid your "Pain to Use" preconception!
If you're wanting something a little more user friendly, then 645 might be a better format. Anything in 6x7 will be pretty bulky aside from something like a Mamiya 7, Plaubel Makina. I'd suggest a Mamiya Press or Universal, or a Koni-Omega but they're ergonomics are pretty awful. IDK. Maybe the later Universals wouldn't be so heavy?
I definitely second the Wista or a TLR. the Mamiya TLRs always inspired me.
I'd avoid a monorail, maybe a medium format monorail would be better, but yeah, I used to think I'd like to use a monorail just for all the movements, but they're pretty annoying to set up and carry around.