Progress!
Wiring complete, standoffs installed as a temporary "case," found an otherwise-nice white oak turning blank with a split, but plenty enough good wood left to make a ~3/8" (9.5mm) sandwich, keycaps installed, and even found a perfectly lovely set of 1" 3M rubber feet that anchor the board down very well, and a good thing too because the aluminum is even lighter than my brain had recognized. I may have to break down and actually lube the stabs, because otherwise the sound is a very satisfying retro-vibe clicky-thunder. Open sides and wads of insulated wiring seem to keep it from being very pingy. I admit though, as a hard-typing, clicky-loving heathen, sound profiles are not really my forte other than "I like it" or "I don't."
I have started on the keymap in KMK, and either I have discovered an entirely new layout, or I completely mis-visualized how KMK would read the matrix. On the plus side, the errors seem systemic and make sense based on what I wired, so I'm confident it was human error in the keymap. All but one keys register something, and with 83 keys on an 12x7 matrix, it should just be that the intentional empty slot is actually mapped to a physical key for the moment. Just hoping there isn't something physical with the fact that I have two "7" keys.
EDIT: Seems at least one of my AliExpress vendors may not know what is "DSA" and what isn't. The reds (I think) are proper DSA, fairly steep slopes on the side and small keytop. The main set looks fine, and the height is within maybe half a mm of the blank reds, but I don't think it's truly DSA (plus it's clearly double shot when described on AE as "dye-sub". The sides are less steep so the keytop is technically a touch wider than my XDA, but the deeper dishing makes them feel more spherical. For my particular look/use case on this board, they are fine to live together, but they're not quite the same. C'est la vie when you're a cheap old cuss. Anybody know if my alphas' profile actually has a name?