Groups and chords
I have referred to George Dillman's group for pressure point studies, but then again he is associated with local dojo's even though there are others who teach them.
If you find the book by Mark Tedeshi, it has some pretty good pressure point and meridian charts for under twenty dollars. Looking at the instructional material, or charts, you will see areas that have groups of pressure points on one meridian, or pressure points grouped in particular areas of the body, in striking these groups with the correct angle, direction, and with the proper form of activation you could go beyond knockouts into the realm of internal shutdown and if not corrected, death.
Hence, concerns for striking particular areas of the body. Some of the oldest knockout techniques of our grandfathers day, clubing or pistol whipping did indeed hit some of these multiple areas on the head, neck, and facial area.
Many times, Atemi for Aikido addresses one or two pressure points to create pain, but don't go farther to understand the knockout possibilities, or immobilizing our opponents with these little buttons of pain.
Maybe we should look at Aikido as part of a larger Martial Arts puzzle to be researched and put together for our own edification.
The answer is out there, but how many pieces will it take to find them?