This is something I thought about awhile back...It may seem a bit off-the-wall, but I thought I'd just post it anyway.
Sometimes I think it's helpful to take a step back and think of the structure of analogies/imagery that underlie a model.
In Socionics, functions are often thought of as sort of like discrete commodities....like, for example, different colored chips that a dealer might hand out in some table game. Maybe Ne is a red chip, Ni a green chip, Ti a yellow chip, Te a black chip, Fe a purple chip, Fi a silver chip...and so forth. Perhaps a better model would be like two-sided chips, where T was just one chip with just one color...and whether it's Te or Ti depends on which side is face up. However, it seems that people usually talk about Socionics more in the first way.
I wonder if an even better analogy would be categorizing organic entities according to shape. For example, looking at clouds...One might look up at the sky and say "which ones are diamond shaped?" "which one looks most like Elvis?" And so forth.
The point is that not every cloud that looks sort of like Elvis looks the same as every other Elvis-looking cloud. Furthermore, a cloud could look kind of like Elvis and also be kind of diamond-shaped. Similarly, I wonder if everyone's Ti or Ni looks like everyone else's Ti or Ni, and whether some people may have N that's sort of Ni and sort of Ne.
Another thing about Socionics is that types are seen sort of like fixed units that act with other units in a fixed way. For example, in the game of rock, paper, scissors, each of these things is always the same, and always has the same relation to the others.
But in reality, I think people may be more like chameleons to some extent. They turn color based on their environment. The question, then, is which color do you *like* to be? Perhaps some chameleons are better at certain environments than others; maybe they have certain environments where they don't have to strain as much. On the other hand, a chameleon can probably change color quite a lot without ever feeling that it's not being true to itself.
Or, you might see people as being like a objects that have different shapes on different sides. If a person interacts with someone who needs the square shape, the person faces that person with the square-shaped side. The square-shaped side of a person is just as much part of that person as the round shape and triangular shape.
Talking about shape, we often see that types apply to the person as a whole...but what if types are simply concepts (sort of like shapes) that apply on many levels? A building may be both circular or triangular, depending on which part you're focusing on. Similarly, perhaps a person may be one type in regard to structure of thought, another in regard to something having to do with content, and yet another that comes out in relation to other people...and so forth.