If you can fund it, I would just get the new Canon 24-70mm f/2.8L II lens. It is spectacular, very sharp, and compatible with full frame camera's should you decide to go that way some day.
I sold my 35mm f/1.4 and 24-105mm f/4L IS USM, after getting the 24-70 II. I have the 50L and 85L II, but rarely use them now. Maybe that is a sign that I need to sell those off too.
I think the best trinity at the moment is: 16-35mm II, 24-70mm II, and 70-200mm IS II. You cannot go wrong with these and your clients will never know you did not use a prime lens...neither will they care! Now, if you like shooting with a bunch of primes, then that's a different story.