If you are going for 12-24 & 24 - 70 do you really need, from a technical aspect, the 16 - 35 as well ?
Alas, I am an A mount user so had to go for Sigma's 12 - 24 ... it is great, so I am certain will will enjoy the results from the Sony FE 12 - 24 lens
I have had the Sigma 12-24. While it was a fun lens to have, I found its usage to be very different to the ones I have for a 16-35.
A 16-35 f/2.8 gives you a wonderful choices of perspectives between 16mm and 35mm. It's the perfect reporter's lens and I found myself needing the 24-35 part of the range quite often. Sure, I also have it on the 24-70, but I don't always have the time to change lenses.
A 12-24 f/4 has quite different uses. First, it is a full stop slower but that is not essential. Second, you miss the useful 24-35mm range. Third, the 12-16mm part of the range is really extreme and is rarely useful for anything else than goofing around. OK: some of the goofy images are quite amusing, but one tires of the effect after a while. The only real professional uses is if you photograph interiors, as it make rooms appear bigger. It is
the perfect lens for the real estate agent, there is a market for that.
Basically, I can see myself traveling with a 16-35 and a 24-70 only. I don't see myself traveling with a 12-24 and 24-70 only. The first pair is actually more useful.