Personally I wouldn't place too much stock in what looks like a photoshopped regular Z1 shrunk down a bit, I'd hold off for some official SONY information before deciding, that way it's based on facts rather than speculation.
You'll also need to apply a bit of common sense. I.E. to fit a body that holds a 4.3 inch screen or thereabouts, logically something will have to give.
Certainly battery capacity for sure, probably the camera module for a lesser one, then there's chipsets & RAM sizes etc too. (You didn't really think SONY will make the mini the same spec as their flagship model did you?)
For me, I'd be happy as long as it's pocketable with a 720p screen
lesser camera module (if I want to take GOOD pics I'll use a proper camera thank you) or the QX10 add - on
I'd go with a snapdragon 600 if necessary
Lesser battery isn't a huge issue, as the screen isn't a 5 inch full HD power sucker, you may find the battery longevity to be similar despite a smaller capacity.
Voice of reason. Mind of a maniac.