This is the sort of thing that gets my imagination going!
A few thoughts:
Rather than randomly picking a Trump card for position #9, how about using the "quintessence" approach for selecting it, by combining the numerical values of cards 1 through 8? I don't use the quint much, but the thing that intrigues me about it is that it relies on the cards already dealt to produce a roll-up or summation of their combined "essence." This makes it a more "internal" than "external" consideration, and a more "organic" one to boot. I'm thinking that the synthesis of the first eight cards would serve as a kind of "launching pad" for the transcendant realization of Card 9. There are various ways of arriving at the quint shown in other threads here.
I was wondering if there is any methodical way of looking at the transition between the pairs of one tier and those of the next, from a tarot interpretation perspective rather than Maslow's hierarchical one. When there's a dual train present, it's kind of natural to "plateau" the sets rather than seeing them as "ascending steps." I'm always looking for the flow in a spread as away to smooth out abrupt conceptual leaps. It almost suggests the qabalistic "Path of the Serpent" for ascending the Tree of Life.
Because it has a branching structure (although it's really more a "converging" one), I was toying with the idea of some kind of "left brain/right brain" paradigm going up the sides (even though that model seems to have been discredited, it still creates useful comparisons). It almost works!
It might be interesting to create three spreads at once (one with just pips, one entirely with courts, and one with majors only), and then overlay them to get a kind of three-dimensional profile. That would increase the level of effort greatly, of course, but it would offer some really interesting insights. You might even create a "grand quintessence" by summing the three top-tier cards.