now, before anyone thinks i have started drinking early, lemme state this.
I really do think the essentials for self defense are in every system, people just have to learn to apply them outside the box.
I am a TKD bb, and I can do just fine in an elevator, by taking the HANDS of TKD and using them
Kenpo can be used for knife defense easily, just adapt the punch defenses for knives. the same rules apply. With grappling? easy, beat them to death BEFORE they can get thier hands on you, and POOF, kenpo handled the grappler.
BJJ people can break arms pretty well, just learn how to do it standing up
my point is that the CORE of any style can be used in any situation. Just think outsde the box
I absolutely see your point and agree that far too often people switch styles becuase they haven't found what they were looking for yet. My key points of contention would be that although all defenses can be used against a weapon as long as you alter some of the blocks at the beginning, the rules are not the same. Hand a knife to an fma guy and try your punch defenses against him, you may end up looking like a head of lettuce on the food network. As for beating the tar out of someone before they get you to the ground I think is naive. Kind of like saying I don't need to practice take down defense becuase I will knock them out with one punch. Jiu Jitsu started standing up and when it was filtered into BJJ took place more on the ground which is where they want it, their underlying phylosophy. So to say to a BJJ guy don't go down to the ground is a completely foreign concept and against their religion basicly.
So I think that you are right if you take concepts learned in any given art and then think outside the box you will be ok, but the CORE of the system will have different phylosophy's and want you to bring the fight to that arena. Also I believe your idea of thinking outside the box is exactly where everyone should be but a lot of people can't do that, they need a road map. Which is why there are only a handful of Parker's, Emperado's, Chow's, so on and so forth. The better you get at open mindedness about the arts the better you are at thinking outside the box, but I believe it is discussions like this that help people get there.