Plan A was to add a 5D2 or switch to 5D3 and get a 24tse as the primary quality landscape lens.
I shoot most of my landscapes with 17-55 at 17 on 7D, sometimes use my 10-20 (when 17 isnt wide enough) but it lacks quality IMO and isnt so sharp on the RHS and corners ( I could get a better UWA but not bothered if I go FF I will add 17-40L).
Now I am being tempted with a 17tse and it can work well on both crop and ff. I can tilt stitch for up to 8mm or so! Downsides is filters and f4 (no biggie there) - and tricky to use on flash bodies.
Not likely to be enough money for both... (for now!).
But I have seen results with the 1.4TC also which look impressive too! (23.6mm or so)