I do a lot of walking/hiking. I don’t like carrying a ton of stuff, and almost never bring a tripod. So my landscapes tend to be handheld wherever I am. I wasn't into people pictures until we had our first kid. Now she seems to dominate my subject matter.
Then the 17-40L is not for you - you can shoot @high iso with the 6d and thus gain higher shutter speeds that compensates for the missing IS, but at the same time you will loose a lot of dynamic range that is important for landscape. And if you're shooting hdr brackets, it's best with a tripod or at least IS so that the frames overlap as much as possible.
Only you can determine if you'd miss the 17-23 range, it's quite a lot, but it's not "general purpose" on full frame and as KR (in this case correctly) says: an uaw lens is not for "taking it all in" landscape but for the uwa effect, esp. when shooting objects near to the lens (the 17-40L has a very good min. focusing distance).
As for the tele zoom, I'd also recommend to have a look at the 70-300L because of it's small pack size (extending zoom) vs. the internal zoom of the 70-200s. Then add a used 24-105L and you're good to go, the overlap of the two lenses is nice because you can skip changing them when outdoors or in a hurry.
As for the 24-70/4: Yes, completely overpriced, near-macro capability sounds nice but it lacks working distance - and the 70-300L has a good max. magnification because of 300mm + small min. focusing distance.