Thanks for the comments.
Sorry for my slow reply.
When I re-started the project back in 2006, I thought of the deck and "accompanying material" as equal partners. Both would develop together, each as part of the other. I imagine this approach differs from other tarot decks being produced today, where artists or "creators" typically focus on finishing 78 cards, then write something about what they did and/or what it means to them.
In practical terms, this meant that I would make a point of understanding as much as possible about what I was doing, and develop reasons for doing things. One of my fundamental goals was to present an interpretation of tarot design and symbolism within the context of a long view of history. The written part addresses that with some degree of depth, and provides a foundation and intellectual background basis for what is seen in the card images. They both say the same thing, albeit in different ways. This is what's interesting to me about making a tarot.
I created the text portion as a series of separate elements that may be shuffled and read in any order, in the same way that a deck of cards is shuffled and read/played. I don't do a lot of actual "explaining" in the text. It is designed to create a series of impressions, and let you connect your own dots. The eleven different volumes each address a subject, and relate to one another in various ways, both intellectually and physically. Some more directly, some more indirectly, and some more clearly via the in-between. So, depending on your disposition, there are any number of conclusions you might reach from this. (This makes it difficult for me to give a short answer when asked what "theory" I follow....)
The art was difficult because it essentially (re)creates a visual language. As far as observing patterns, that's a difficult question. I spent about a year working out a system for the pips that was rooted in the traditional pattern, and then a few years figuring out how to execute that system as my own card designs. I hoped to produce a result that had many layers, but not so it felt contrived. In the end, I don't feel that I've invented anything particularly new, but rather enhanced what was already present in a well-founded interpretation of a traditional design. I wanted to make something that someone a few hundred years ago would have no trouble understanding.
What surprised me most is how far out in the countryside that I find myself now.