Looks like you're getting lots of feedback--that's great.
I agree with the folks who are saying that the Schneider/Rodenstock glass on a technical camera will outperform any MFDSLR.
Like yourself, I started my venture into digital medium format with the intent to maximize image quality. I felt that the Arca-Swiss 6x9 F Metric w/Orbix would be the platform of choice, but quickly realized it wouldn't have the versatility of an SLR.
My first compromise, I decided to go with the SLR first and eventually pick up a solution which enabled movements/view camera glass later.
Interesting what you say about your left hand. Most of the cameras (H-series, Hy6/AFi, Mamiya) will allow you to grip with your right, and adjust exposure with your right as well. If we assume manually focusing with your left hand is off the table, you'll need a camera with a mature AF lens lineup. One exception to this is the Hasselblad V (500-series) camera. It's designed to be supported by the left hand and all focusing and exposure operations done on the lens with the right hand.
The good news about Hasselblad V is that every back is available for it, so you'll have a smorgasbord of choices. Let me give you a quick run-down of my experiences and some of the key issues I ran into with each of these systems (I've owned all of these): (Others experiences may vary)
+ Perhaps the highest resolving optics outside of large format (I say perhaps, because I did not get to try my Rollei Schneider glass on a Phase back--my current back is slightly lower resolution (-6%) so I can't make an apples-to-apples comparison)
+ Purely mechanical - could fix jams, etc, in the field, less susceptible to rain, no batteries required
+ Superb build quality, handling, and use (once you get used to it).
+ Any back will work on Hassy V.
- External sync cable required - fragile and finicky; made changing lenses that much less fun. Incomplete exposure metadata in image files.
- Cannot change image orientation without removing back; spitting rain, dust, and changes even on bright sunny days gave no end of sensor dust
And my biggest issue (probably the biggest single reason I'm not still on this platform):
- Hasselblad 500-series aperture blades give very disturbing pentagonal bokeh; It really was a dealbreaker for me. I still have samples if you would like to see some of the results. Note the Hasselblad 200-series camera's FE lense lineup has round apertures, but very limited digital back compatibility.
+ More modern or "conventional" SLR design (eliminated sync cables, provides full exposure metadata in files, etc.)
+ Most affordable solution?
- Personally do not like the HC-series glass for landscape (not optimized for infinity, similar bokeh issues to Hassy Zeiss 500-series CF/CFE glass)
- V-series glass adapter/H-camera forces left-hand use for cocking shutter and operating lens rings (lenses are designed for right handed operation)
- Among the heaviest solutions
+ Smaller, more compact "conventional SLR design
+ Lots of "energy" in this line from Phase One
- Mamiya glass underwhelmed (build quality in particular, but image quality didn't stun me either)
? Perhaps worth another look once Leica leaf shutter lenses become available?
Sinar Hy6/Leaf AFi:
+ Best-in class ergonomics (tilting handle, rubberized body, once you try Sinar's rotating adapter you won't ever go back to removing the back to rotate--Leaf has an upcoming rotation solution as well.)
+ Great lens lineup, Schneider perhaps just a hair behind Hassy's Zeiss for resolving power, but overall far ahead in terms of overalll rendering quality. Plus, both Zeiss and Schneider lenses are available, so you can pick from the best of both worlds.
+ Some high speed glass (50/2.8, 80/2, 110/2, 180/2.
+ Good AF lineup
- I found both the Leaf and Sinar backs to be noisier than the Phase at low ISO (the situation was reversed at high ISO, but I am a low-ISO shooter)
- Weight - the camera is feather-light, but the glass weighs a lot.
I currently have the Hy6 and am very happy with it. If you're looking at economical solutions, be sure to take a look at the recently announced Hy6 65R.
One other platform to consider is the Contax. I've never owned this one, but was within a hair's breadth of doing it as I was leaving the H2. It has Zeiss AF glass across the board and can be had very inexpensively. Apertures are well-rounded so no bokeh issues to worry about. It's not well-supported any more, and some of the back manufacturers have dropped Contax mounts on their latest digital back offerings, so beware.
None of these guys are weather-sealed. The Phase and the Sinar don't have vents or fans, but the Leaf does. This initially pushed me away from the Leaf, but I may end up with a vented back unless Sinar's version of the AFi-II 10 is passively cooled. I don't like the lack of environmental protection, but it is something I can manage until someone provides a better option.
Both my Phase/Hasselblad and my Sinar Hy6 have been used in Pacific Northwest rainforest rain, and in alpine (mountaineering) cold. I protect the equipment appropriately and have never had any issues.
When evaluating your system, don't underestimate the savings that can be had by looking at the used market for lenses. This could make a huge difference in terms of the system you can afford.
Not so easy a decision, eh?
Remember to have fun with this,