6 of one, half a dozen of the other Craig.
Iow, as I gathered from your post on the kotegaeshi thread, if one has the kuzushi correct then there should not be a problem of taking up slack... on the reverse side, if one focuses on taking up the slack, then the resultant kuzushi should be effective and correct. Makes sense to me.
Imo kuzushi should be applied instinctively like the rest of any effective technique (preferably during the avoidance phase), so I guess the practice of effective kuzushi drills can deal with someone's inability to take up slack in his/her basic technique.
Just some thoughts.