Thanks for your posts Chris. I started this thread with an example where I grabbed the arm of someone trying to punch me. I had goals of controlling their ability to punch me and at the same time the need to throw them to gain time to get away. Fitting the examples you give to the situation I would have been uke and defending myself from attackers.
My point was that I don't think aikido folks train for grabs that are intended to really so something. Ledyard sensei's post (#10) does a better of explaining this than I do.
I think this thread is going away from where you originally intended. Maybe someone will start another thread to address what is being discussed now. Sorry for the hijack.
If you are boxing with someone (unarmed), the common boxing cover is a far better practice than wrist grabbing. The boxing cover allows you to move into range, limits the damage the other fellow can inflict on you, and allows you to land a powerful blow with either hand.
If you want to bring them into a control position (top mount etc) than simply shooting in on them, gaining a double leg or if you miss getting a waist lock or bear hug, than applying a take down into control position is a favorable strategy.
Wrist grabbing, as a non-transitory technique, in an unarmed situation is not the best idea, so there is no real need to train for it. That's why we don't see much training for this in MMA gyms. A wrist grab is only a needed to control the hand specifically, which is seldom needed unless someone is armed.