I think what you are asking is stated in this, you train atemi, you use atemi. What is difficult to understand about that?
Nothing at all, but my questions is so simple a child can answer it. What are you doing to train atemi?
Lets try this out.
I'm a white belt, I ask you what I should do to practice my atemi. Are you going to tell me to practice awareness? What are you going to tell me?
If you tell me practice my awareness, I am going to then ask, what can I do to practice my awareness to improve my atemi?
Then you are sticking with the "it doesn't matter what you do, as long as you are mindful." I then submit that you are wasting your time training aikido. You already know you just need to be mindful, so why not use your time somewhere better spent? You are not learning anything that can't be learned working a spare job for cash, helping be a big brother or sister for kids in trouble communities, etc. You can do all that mindfully and be just as competent in self defense.
At this point you have basically told the white belt no useful information, he is not going to get better, be discouraged and quit. In the context of this conversation, you are not adding anything and are in no way allowing anyone to learn from or analyze your methods and comment.
The core question is, what methods and drills are you doing while you are mindful which improves your direct ability to punch a person in the face when he is trying to hurt you? Without an answer, I can only assume nothing. Which leads me to assume you are making an uniformed statement based on the stories of a long dead man.
Like I said, I will go to the ground with the grappler, because I can hit him, but my awareness is not good enough to make sure I hit the "button" first time every time. I do believe that with consistent hard mindful training that you can develop the awareness required to do this.
Again, what kind of consistent mindful training? Are you really saying playing chess, painting, walking the dog, jumping jacks, will improve your chances at hitting the button?
However, you have posed a new question with this. How long do you expect it to take to reach this level? Is this time well spent if your goal is being able to defend against a grappler? Are more direct methods of defense against a grappler (such as bjj, judo, etc) not going to foster the same awareness? If the answer is no, then what do you think is missing from their training? What would you add to improve their training, or is it hopeless and can only be done in an aikido practice? Which leads back to the first question, what are you doing when you train?