It's okay and interesting to organize information about behavior patterns. But if you commit too seriously to a certain number and order of Types, then you're ill-prepared to respond to the reality of an ever-changing and fluctuating spectrum of human behavior/feelings.
That's a good point. I can think of many occurrences in my life and in others' where I've seen an abundance of structure weaken that primal sense of spontaneity. See: Aneristic Illusion etc etc.
The positive side effect, I've found, was dropping a sense of guilt I've felt whenever I'd try to improve myself. I always felt it was 'selfish' but now I see the benefit of doing that...
It's true, improving yourself in a proper manner will, in a roundabout way, help others.
Then again, if you see the benefit of improving yourself because it helps others, then you are actually valuing the sake of the others. :P
I don't think that's so bad. I'm about thirty-one now and for the past year I've decided it was time to finally formulate my own Purpose (perhaps even to a higher ideal ... but that just sounds kinda silly). I call it my Master Plan (perhaps that's even sillier). And something I've recognized as a component to that is a certain degree of service to others. Maybe that's just the father in me.
One thing that does seem to make sense is that without others, I don't think I'd have quite the same sense of self (if any) that I do. And so removing others from that equation, I'd also be removing a key component to my own sense of self.
So why not? They say if you want to learn something really well, teach it. Sounds like a good plan to me.