I´m amongst those who are not too fond of the 16-35. I have actually just sold mine. For UWA I use a Zeiss 15mm or a 17mm tilt&shift. In my opinion UWA does not work with people in the frame, unless they are at the center of the image, due to distortion. The 17-40 f4L is a very good alternative by the way, quite a bit cheaper, but a stop slower.
So I would rather have (order of priority) 24-70 f2.8L II (or consider the Tamron with stabilization to save money for a prime), 70-200 f2.8L IS II and then a fast prime, preferably 35/1.4 or 50/1.4, where Sigma probably are best price/performance wise at the moment (provided it is the newly announced 50/1.4).
But as more than one has advised you already, you need to make up your mind yourself. Rent or borrow, try it out and figure out what suits you. We´re all a bit different from the other nut-cases