How could he replace Williams? While Williams isn't looking like a good fit on the Cowboys offense (I think this is more a head thing between Romo and Williams than anything else), Cribbs doesn't provide the talent at receiver that Roy Williams does.
Cribbs is a special teams player, and a fun weapon to put out on the field between the 20's. How much value has be showed at the goalline when trickery becomes less productive against good teams?
You simply don't build your offense on this kind of talent. Guys like this have a place in the NFL until they start thinking they deserve big money when they simply don't. Of course, in the real world, we would all jump all over a Million Dollars to go play a game.