I have the 24-70 II and 14mm. Both are excellent lens as is the 24 II (which I don't currently own). However there is a gap here. the 17 TS-E would fill the gap but it is big, heavy, cumbersome and expensive if only used as a straight 17. There is the Nikon 14-24 but it is awkward to use (though not impossible to use).
Other recommendation? Nothing in the Canon lineup seems to fill the gap without giving up on IQ. Any recommendations.