Glady, after regular training, randori (up to 8 ppl so far), sparring with other martial artists, and real life situations (one on one to a group of 20 ppl) I've been in...I've realized an AIKIDO technique with atemi is a waste of time. It destroys its effectiveness as a martial art. Atemi to me is using a strike, or what Aikidoka call strikes before the throw or pin. To other martial artists the atemi we use is kind of a joke, but that's another issue. If you talk about yelling or something else that to me is Kiai or energy, which you need a lot of in Aikido and in life.
Now striking in general, punching, kicking, etc. IS effective, so I'm not saying attacks are ineffective but attacks with Aikido is. In randori, multiple attackers 2-8, you have no time for an atemi AND a throw, only a throw OR atemi. But you can't exactly render an uke unconscious in class so it's hard to gauge the effectiveness of your strike during randori. Aikidoka aren't renowned for their superior strikes, it's something that's sorely lacking. You better throwing your attacker into someone else and controlling the crowd.
I have been cross training for about 10 yrs now and when I spar people of other martial arts, their reflexes in kicking and punching are much faster than the average Aikidoka trying to use atemi. They are always beaten trying to go toe to toe with someone who SOLELY practices kicking and/or punching. After changing my strategy though, which was to drive in close for Aikido I became much more effective in using JUST Aikido. And when you're that close you have only time for one answer, throw or pin not play with your partner. Once the response was instantaneous you leave no gap for people to respond or get away, and since they are use to fighting people at a certain distance they do not have an answer to your technique.
In real life, it was the same principle. Don't waste time, do your technique fast and get them on the ground. I have struck someone before, but I did not call it Aikido. It was just a response. But the next situation I remembered my principles in Aikido and brought the attacker down without having to hit him, by then his friends came and apologized for him being a drunk idiot. Usually I avoid fight situations but I have a weakness for standing up for other people when they are being bullied, especially females.
As for BJJ, the goal is to subdue an opponent with a choke or pin, they don't control positions, they flow with the persons movement and find an opening for a pin or choke. JUST LIKE AIKIDO, just on the ground. ...and more training against resistance.
So in their practice it's important to have superior technique, not use atemi to get the arm bar. It's to move in a position to get you to expose a limb so they can take it and lock it. It's fun! You should try it sometime.
Speaking of "real situations" and responses, here's a great video that should illustrate a good point about real life. I think we often misrepresent real life with movies....