OK then... Poll over, and the only thing that stood out from the poll was to have thumb keys.

The most important thing we got out of it is that it is much easier to reason about a real proposal ... so here it is:
The idea is to create a split symmetric stagger keyboard, like a western answer to the
µTron but with Cherry MX switches and regular key spacing.

- westron.jpg (35.48 KiB) Viewed 3939 times
The µTron has non-standard diagonally slanted thumb keys. To make up for that, I instead rotated the keys, and I picture that they would be mounted upside down so that they would slant towards the thumb instead of away.
The only unusually-sized keys in this layout would be the 2u Tab and the 1.25u home-row keys.
However... if you instead value function keys higher than thumb keys, you could rotate the keyboard 180° and mount a more traditional layout:

- trad.jpg (35.7 KiB) Viewed 3939 times
I picture the internals as being much like the ErgoDox. A double-sided 8×6 key PCB for both left and right with support for both PCB-mounted and plate-mounted switches, through-hole or SMD diodes. You practically get support for Alps automatically with a double-sided PCB - only the rotated keys and a possible ISO Return key option would be tricky.
A Teensy in one side, mounted under the next-to innermost column, but with the port sticking out. An I/O expander in the other side, but not at the opposite position of the Teensy but at the opposite position of an EEPROM chip for storing macros.
That is the idea anyway. I anticipate that there will be a few tweaks here and there to make it work.