Triple threat is what we're looking for in the spread. Smart-Pass-Run QB (and in that order). When you assess the arm and feet of a QB... make sure you've included his head.
And in reality... our personnel this coming season fit getting the ball distributed to them. That has little to do with the QB's legs... and whole lot more to do with his arm and his head. When a smart QB starts delivering the ball to the 5 to 7 options on the field... it seriously spreads out the defense. And to me... in order to keep that QB healthy for the entire season... I'd like his head to open up wide open spaces to run and slide for yardage. Defensive players are starting to eliminate a full season of injury-free running back QBs.
We aren't running a pro style set, even with Haack. And don't think Haack has concrete feet. If he's a heady QB... he'll create space to run that will damage the defense exactly how the play is drawn up to do.