anyway i think i have this thing 99% figured out. something that stumped me for a bit is the bus connector here. all the signals are passed through from the Amiga side (blue/green connector) to the card edge side (going to the next sidecar expansion) with two exceptions -- see the weird pins that stick out.
the first pin is a CONFIG_IN# signal that comes on pin 12. if it is ground, then the card decodes the address space at E8xxxx -- the Amiga autoconfig space. this pin is always grounded on the A1000. once the card completes its config, it remaps that space to somewhere else in memory, and then pulls the CONFIG_DONE# line low, signaling the next sidecar expansion to do its autoconfig.