Most of the martial arts that I've been involved with over the years have had sets of goshin jutsu, or situational self-defense techniques. You can sort of think of goshin jutsu as a concession to the folks that are forever asking, "Well, what if he grabs like this?" or "What if he kicks like this?"
Often these goshin jutsu sets include situations that aren't otherwise commonly practiced in the rest of the system. For instance, the Kodokan (judo) goshin jutsu includes defense against kicks and various weapons. The Tomiki aikido goshin jutsu (koryu dai san) contains clothing grabs, chokes, and seated techniques that we seldom practice outside of that context. Often in karate classes, the goshin jutsu sets will be heavy on grappling defenses, assuming that the typical mode of practice is more kick-block-punch oriented.
These sets of techniques are usually relatively small - maybe twenty to fifty techniques, and as such they are meant to be representative instead of comprehensive. You can't really come up with a programmed response to every possible "what-if" situation, so a set of goshin jutsu typically deals with probable situations instead of possible situations.
I've been thinking about goshin jutsu a bit lately, and something that has caused a bit of head-scratching is, what is the role of goshin jutsu in our martial arts? See, you can treat each situational technique as a distinct kata to be performed just so. This is sort of the approach that the American Kenpo guys took - they have dozens of short little pseudo-kata, evocatively named things like "clutching feathers" and "gift of destruction." They call these things self-defense moves (so they are goshin jutsu) but they are practiced and tested and performed as if they are kata. They seem to have evolved from goshin jutsu into kata over the years.
Most systems that do goshin jutsu or self-defense sets, seem to take the same process of kata-fying (codifying) goshin jutsu until it becomes kata. But that seems to lead in the direction of the American Kenpo guys - dozens upon dozens of kata-like situational self-defense moves.
Although I generally really like American Kenpo, I don't like that aproach to goshin jutsu... too much to remember... too technique-based instead of principle-driven.
So, how can we do goshin jutsu and not slip down that path to technique multiplication?
How about goshin jutsu as randori starters? Randori matches that begin in one of the goshin jutsu situations. So, after the initial attack/situation the randori reverts to normal aikido toshu randori rules wth both players active, and the partners play out the scenario. Then, however it ends, the partners switch roles, set up the situation again, and go again...
I suspect that goshin jutsu situations, if they were randoried sufficiently, would result in a lot of the same termination points as found in the canned goshin jutsu sets - just because many of those solutions are highly efficient, but this manner of practicing them should result in the practitioners getting much, much more practical experience than if we were to program the responses and run them like kata.