Good food.
I am really looking for that small form factor for "party shots" & Street types vs. foisting the 5dIII in someone's face, etc, etc. and you do the M great service with comparisons.
I wonder if the A7r might not be the compromise (which means it doesn't do anything best perhaps) could still use all the C-Glass, it would likely have a pancake at some time so it will reasonably small, and yet have the uber resolution to use the existing glass investment - how often would I really reach for the 5dIII???