You see, there's absolutely no need for the right-hand-only button placement on the back of the 6D.
Before articulating LCDs, even the Rebels had buttons on the left side.
So, having buttons only on the right side is not some novel ergonomics idea.
Canon did it so that the 6D has a consumer feel to it and is different from the pro-oriented 5DIII.
This is so-o-o obvious that mine opinion really disproves yours in this case - based on the obviousness criteria.
And btw, you should be worried that such an obvious thing escapes you.
What escapes me is why having buttons on both sides is more upmarket than having them all on the right. I've been using my 5DII and 6D interchangeably a lot during the past week and - perhaps because I'm a mere "consumer" - have no hesitation in preferring the layout on the 6D (dare I even say I don't much like the joystick). But it's easy enough to get used to either (one could even, I suppose, get used to Nikon's horrible ergonomics).
+1 million! I agree wholeheartedly (obviously). Nikon has terrible ergonomics, and coming from a XXD body that had buttons on both sides, I got used to the ergonomics of the 6D in about 1 minute. And at that time, I decided to sell my XXD body, because even though I had loved it for 4 years, I suddenly felt no need for it anymore.
Using the 6D feels like an extension of me, and that didn't take long.
I frankly don't wish the 6D had anything different than it does. I am mostly a stills shooter. If video was important to me, I would certainly own the 5D3 and install the ML RAW video hack...
I've never had a real problem with any aspect of the 6D's autofocus. And it's not like I don't have experience with bigger bodies. I have used the 1D4, the 5D3, and the 1DX (hope to use it more). Also, I fail to see the logic in owning a "backup body" for someone who is not doing professional (event) photography. I mean, I do pro work on occasion, but even I don't currently own a "backup body". I don't feel the need for one. I use other compact cameras at times (decent ones, not cheap ones), but I honestly don't feel out in the cold having just the 6D as my only DSLR body. If I had a team of other photographers working with me or for me, that would be different. Or if I was making say $1k a day, 3 or more days a week, that would also be very different.