In addition to a question, I may have a partial answer to offer.
In my home dojo, we do a lot of grasps - wrist grasps, chest grasps, etc - as beginners, as I'm lead to believe is common in other dojos.
It seems that grasps are useful in that they can be done committedly without causing harm. You can still do drills like "If I get my hand out of the way, I'll do this; else, I'll do this".
I remember one exercise that pointed out a weakness in our practice, at least amongst beginners. Often, if uke knew that it was going to be a technique where shite (nage) pivoted his/her wrist out of the way, if shite stood still, uke would end up reaching waaaay past shite's hand, sometimes even bending over a bit, and looking confused. Good reminder that uke's going for the wrist, not trying to lean over so he/she can be thrown. ^_-
Of course, it doesn't have that same 'intimidation' factor that a punch does, so it can't really serve to rewire that instinct in the face of imminent harm. Nor is it a 'real attack' in the direct sense.