I would go with the 24-70 II and add one of the primes later if you still feel a need for a faster lens.+1 Good advice. The 24-70II is so good it has prompted plenty of photographers including myself to sell L primes in the 24-70mm range. My 24 f/1.4II has gone as has the Sigma 50 f/1.4. If I had a 35 it would be gone too. The 24-70 f/2.8II is a simply awesome lens and makes primes in this range all but obsolete.
the 24-70II is great. however i'm not sure i'd agree fully with what you say about replacing primes.
i myself love to be creative with shallow dof so fast primes are still very desirable and useful for me.
photography is my hobby not work so maybe thats the difference..