I got a bit further - I found a trace that had been eaten through, patched it, now the Mac starts off both keyboard and back power button! Unfortunately, still no video or boot though.
That indicates to me the possibility of more traces.. but so far I'm not seeing any that are obviously suspect.
I will note that while I can power up with the keyboard button, I cannot shut it off with that. Only will shut off with the back power button.
I finally found the trick to getting an 8.1 System suitcase to recognize HFS+ is including the 'Text Encoding Converter' extension! But this is 592K and the 8.1 System suitcase is more than 6M... I'm still searching how to slim it down.
At least it will fit in a 12M disk image, so it should fit on the 8MB ROMinator II...