I fully understand the appeal of an f2 zoom, don’t get me wrong, but is the combo of a 24-70 f2.8 and 2 good primes opening at f1.8 or f1.4/f1.2 not a better solution for a large majority or cases?
I make my money photographing people and I'd prefer a 28-70mm f/2 to a 24-70mm f/2.8. 24mm is too wide for me- it looks crap photographing women because perspective distortion is almost unavoidable in UK-sized shooting spaces. 28mm is usable with care for wide shots, but by 24mm you almost inevitably have nasty results.
Other photographers with other working patterns might differ, but I'd actually RATHER not have that excess 24 mm on the wide end, and have f/2 instead.
So I'd definitely take a 28-70mm f/2 plus a fast 85mm as my basic shooting kit instead of my current "go to" set ups of 24-70 f/2.8, 28mm, 35mm, 55mm, 85mm if the quality was there. Longer at the telephoto end would be better, but 28mm is way better for me than 24, and I wouldn't cry if it pushed up to 30-plus too much.
My dream all in one lens would be a 35mm-135mm f/2 zoom with stellar optics, in fact. But physics probably forbids.
Obviously, it depends on the optical quality, weight, etc.. but having at least one set up in the kit cupboard which avoids lens-swapping for dusty environments is always good so a two body set-up with a 28-70 f/2 and a 70-200 f/2.8 would hit the sweet spot for me personally.
Cheers, Hywel