Power Supply! Along with the usb serial I also received a usb to barrel power connector -- I tried that first. It works,
Theory:
It looks like a brown-out.
Supporting Data:
While the system is first booting it looks fine until... the radios fire up, then there's enough of a current draw to cause a voltage dip and crash the OS. (no radios during unbrick, so, lower current?)
Would love to power test the ps, also watch serial during boot and measure current draw, but hey it's working --
thanks for all the suggestions!
Peace!