This is where I think you have it wrong. Historically four year players from big programs fall in the draft because in most cases they've reached their maximum size and their game, for the most part, is what it is. But these are the players, the Arenas's, Maxiells, Stuckeys, and such, become solid role players in the NBA.
Our "project" players didn't come from big programs. They didn't excel at the highest levels. They are projects because they are bang or bust. A guy like a Sam Young, or a Danny Green, they are four year players from major programs in major conferences. They have a history of showing up big, in big games. These are the types of players you want rounding out your rotation.
I'm willing to bet, right now, that Young or Green could already leapfrog Walker in the rotation. They are both phsyically good size for the NBA. Both have a good 3 point shot and play smart team defense. And they both can finish around the rim and hit a 15 footer.