I'll take A7 FF mirrorles and Zeiss lenses in this case I doubt that an A7 with the 24-70 is smaller or lighter than my existing setup so it would end up as an even more expensive paperweight.
An A7 or any FF mirrorless camera is still going to require large, bulky lenses once you move beyond a few small primes in the wide to normal range. FF Mirrorless systems are a great (and very expensive...) portable option if you want something limited like an RX1 with its fixed lens or an A7 with a small prime.
But, when you move into the full system arena, they lose almost all of the mirrorless size advantage since the lenses are the same size as DSLR lenses. Unless you plan to just use the A7 with small primes, you need to invest in a full system of Sony or Zeiss lenses (UWA, 24-70 zoom, 70-200 zoom, 200+ tele, fast primes). At that point, what have you gained over a 5D3 or D800 and compliment of Canon or Nikon lenses? A few hundred grams in camera body weight? What are you giving up to save those few hundred grams of weight? Quite a bit in my opinion given the lack of native E-mount lenses and Sony's dubious record of changing lens mount systems every few years.http://camerasize.com/compact/#487.392,380.294,ga,t