A 'disciplined' imagination just doesn't seem very imaginative, or productive, to me. If your thoughts only go where you want them to go, I'll bet you VERY seldom experience a EUREKA! flash.
J'C: "You seem to be confusing discipline with control or repression. A disciplined imagination can go wherever it wants but knows the difference between imagination and reality. It can go to the farthest borders of fantasy, and can even suspend disbelief as needed, but the tether to reality stays in place and the fantasy is never confused with what is. This is not to say that one can not learn from fantasy, the eureka moments are common and useful. But finally they get pulled 'back to the lab' to be tested against what really is."