I don't think anyone's brought up the Triad idea of the Enneagram yet - it's the idea that you default to a lower (or a higher) function depending on how healthy you are:
http://enneagramtriads.com/html/the_18_triads.html
Each number has a triad: 1-4-7; 2-5-8; 3-6-9...and all combinations in between. If you're a 6, you can "act" like a 9 if you're comfortable with who you are. In the same way 1s can act like 4s when they're unhealthy, and so forth.
I wouldn't take a lot of stock into it, but it is an interesting take on the Enneagram and how we might test one way but act another.
Interesting... because I've continued to research the Enneagram types, I am now strongly leaning toward my being a
1w2. I was mistaking 9's need for tranquility for 2's love need, just like I was mistaking 8's assertiveness with 1's drive and perfectionism. As proof of my 1 type, I rarely post without editing my errors at least once. My 2 type is evidenced by how I'm always trying to help others, but it is a wing because I'm more concerned with the truth than a bedside manner.
However, now that I have realized my type, I can attest to the validity of your theory. 1, 4, 7, 2, 5, and 8 are all pretty good descriptions for me, and in that order. 1 with 4 and 7 are my base reactions/mechanisms, while 2 with 5, and 8 are my secondaries... kinda like how Ni and Fe complient each other, but my Ti and Se are also strong.
From what I have read, most people have one main fear that drives their defense mechanisms and needs, but some of us have more. Most people are at their core a balanced Enneagram type. Some people have a strong wing, and others have two strong wings. Because my issues are so deep, my Enneagram personality traits are also very broad. This implies that there is a hidden connection to cognitive functions... not with respect to the order of our functions, because function order is unrelated to our fears, but to the degree to which we develop our functions since stress
is the greatest factor in function development and stress is a byproduct of our fears.
This makes me consider the possibility that the width of someone's Enneagram base is proportional to how well developed their cognitive functions are.