I owned the 17-40 for a number of years when I was normally shooting a 1DmkII crop. It has better performance and is less expensive than the 16-35/2.8 version 1. However when moving to a full frame body I found the corners/edge performance of the 17-40 frustratingly soft.
For several years I have shot with the 24 TSE II and 17 TSE lenses, both are really terrific. However, I do not necessarily see the 24 TSE II lens alone as replacement for the compositional flexibility of a WA zoom. Whereas shift may be fine handheld, the TSE lenses require a tripod to properly use tilt, and close inspection of the LCD in Live View is mandatory. Getting close to the focal plane can provide an unusual, dramatic angle with lots of foreground, but this low to the ground angle won't work for every WA scene. Although I seldom carry a zoom, I have plenty of primes to cover all focal lengths.
On the other hand, for WA landscapes, TSE lens shifts facilitate 3 shots panos, essentailly doubling the angle of view. Why don't you rent a 24 TSE and see if it is your cup of tea? They do take quite some time to figure out tilt movements though.