I watched some of their spring game. The other two QBs ran the offense better than Heaps because they are dual threat QBs. You can't run a spread with a slow QB. When Heaps ran the read option, no one respected it because he wasn't a running threat. The read option is the bread and butter of the spread. If you can't run that play, you can't run a spread offense.
I feel bad for Heaps because he went to KU with the impression that Weis would run a pro-style offense.