I'm partially believing in your article, and partially believing that there is a foundational virtue.
I say this because normally analogies fit the inner world. All parts of a house are equally parts of a house, and incomplete without the other parts, yet still has a primary foundation which holds all the less stable grounded parts up.
The question I would then pose, is if any virtue is more analogous to a foundation than another.
Right now, steadfastness seems the most analogous to me.
Actually, we could just say something like "foundation of character" without having to use another word.
Addition- Then again, there is no reason to assume a house is a proper analogy. Like, what if we used the humam body as an analogy. It would be wrong to say our legs are the foundation of good body since it holds the rest of the body up, nor more than it would be right to say the hands are foundational since we can't eat or manipulate nature (realistically) without them.
Your probably right in the end.
Addition- I just remembered that some buddhists talk about the Dan Tien (the chi center below the navel) as being foundational and if attention is kept there one will have maintain fortitude.