i consider when you teach a student more in a athlete-coach relationship, to be best for the intermediate/advance level. the reason i say this, is because you cannot look a fighter up and down in the beginning, and say, well you are skinny, so i will work on this and that, or you are slow, so i will work on this and that with you.
its just like people who say, tae kwon do is for tall people with long legs, southern style kung fu is for short strong people, etc. is that saying a small skinny guy will never learn to grapple better than a big guy? no, and a student who comes through the door slow and strong with no leg flexibility, might end up as a lightning fast kicker. for beginners its best to teach him the basics of everything, then as he develops and learns the basics of each style you teach, then let him specialize. sometimes i pick what i will focus on with intermediate students, sometimes i will look at what is his favorite way to fight, and build up that.
its important for fighters to at least understand and be able to use the basics of each style you teach before you or him "pick" one. this is how you become a "complete" fighter. he learns many styles, and then picks a specialty he can use to fight against all of them. i agree that its not good to use one size fits all with your students. i also think its not a good idea to just pick one way to fight, and not show him others before you get a good chance to see what works best for him.
but i dont see anything wrong with one size fits all for beginners while you build there foundations. but after he has a few years, he should specialize in something to take to the advance level. if he tries to specialize in too much, none of those skills will ever see the potential he can reach.
which leads me to "concept approach". some teacher spend too much time on "concept". concept is good when they first learn something, so they can keep it in the back of his head while he's learning to do it. but after a while he will need "hands on", lots and lots of repetition, then lots of lots of doing. one thing i see a lot of, is people who want to demonstrate everything, with demonstration speed and demonstration power. so they say, "feed me a number..." what is more of a display of skill, is when he can say, "spar with me, and watch out for my ___ technique." and then hit you with it. when a tennis player is showing you his secret weapon, he does not tell you to hit the ball to him once, you have to play the game. "concept", is good for the fighter to understand what he is doing, but it is a very small, thing that should be emphasized. instead, people make there whole system of concept of this style and that technique. to me, "concepts approach" is like saying "collection of techniques approach".