Well, yes, according to that flighty intuition I had we'd differ there. But it was just that; a flightly intuition, not anything set in stone. It would work only when the slave personality was opposite in static/dynamic, so the number of possible types would be cut in half.

The best way I can explain it is using smilingeyes' mechanical/mathematical socionics system;

According to MM socionics combinations of functions can be defined in atomic sentences on an object subject relation as interpreted by a person of the type that holds said functions:

ISTj, for example, becomes:
I am subject at the moment,
Object-of-thought is object and has clearly defined capability [x].

This roughly translates to: I act, right now, based on a piece of certain knowledge that I hold about a certain object. (possibly myself, which in turn would mean: I do x because I can.)

So that summarizes the ISTj mentality.

Now the important thing is that the ISTj is a static type. For the dynamic types the object/subject relation is inversed. ESTj, for example, means:

I am object at the moment,
Object-of-thought is subject and acts in clearly defined way [x].

Which translates into: I am forced to react, right now, by an object the actions of which I presume to have clearly defined knowledge of.

(I should add to this that according to smilex the now vs. the future is actually another way of defining well-defined/not-well-defined in regard to perception, which was otherwise difficult to put into words.)

What intuition told me was this: If I choose to act out of my own volition, I am immediately met with the problem of how I should act. The problem logically can not be solved from a purely 'proactive' mentality, so there MUST be a reactive mentality to complement the proactive one.

So this line of thinking is based on two things:
- smilingeyes' intuition that socionical type strategies work roughly this way, (which is also implicit in the sexual attitudes descriptions)
- my own intuition that I describe in the paragraph above.

Is the complementary personality fixed relative to the main one, or independant of it? That would be a topic for speculation.

About the type suggestion; INTj-ENFp makes an awful lot of sense... (although I don't have an obsession with knowledge at all, beyond that I am very eager to find ways of putting worded knowledge into formal terms to combat my uncertainty (or rather to end fruitless discussion amongst people))