Well the issue there is that the wrist twist is actually a small part of what makes the technique work. The real trick is to get your uke in a position where you can settle your weight over a point where they can be unbalanced. The "lock" really just serves as a mechanism to maintain connection with uke's centre.
I think this picture illustrates my point:
http://members.aikidojournal.com/wp-...kotegaeshi.jpg