It would be missing more than half of the sensor.and that's the only thing 6D offers. better IQ and ISO. 7D(2) on the other hand:
- AF speed, spread and points
- 100% VF and 1x magnification
- more custom functions
- better weather sealing and durability
- (Dual, +?) Digic 6 processor for the 7D2
- the tag "TOP APS-C"
and the list goes on. i completely see how its priced above 6D, even though i would rather see it not get above it. but in 1 year time, when 7D2 is supposedly released, 6D's price will plummet due to its age and.. you know the rest.
Interestingly, except for CF as a difference, your list sounds a just like a comparison between the 5DII and 7D. Which of those was more expensive?
Keep in mind the timeframe. Five years ago FF was much more expensive to manufacture than it is today. The fact that the 6D, still relatively new, sells for as little as $1700, is quite telling here. I am not sure that a comparison of the 5D II and 7D from four to five years ago is good enough to predict the future in the case of the 6D/7DII of next year.
The two cameras are different, for sure...but that does not mean they don't both qualify for the same level of "pro" gear. Functionally, the 7D II (at least as the rumors stand now) sounds like a much more professional, higher grade part than the 6D...regardless of what the numbers may seem to indicate.
I still see "Not having to buying somewhat expensive non-EF-S standard zoom and comically expensive longer glass" as a huge selling feature that is worth driving up the price of the 7D2.
As much as many folks on this forum believe there is a not-so-subtle attempt by Canon to push all 'gear spenders' into the FF column, isn't there also value in selling a very pricey rig that obviates the need to buy new glass? Clearly, capable shooters would pay a premium to get state of the art gear without having to make the FF plunge.