First off, bplan DOES answer emails. Have you actually tried or just making things up? There is a thread on here from last week where a guy got his peg2 board repaired by bplan.
Secondly, the reason nobody has posted a list of firmwares is because i'm sure they dont want emails saying "you ruined my computer" because upgrading firmware can be dangerous.
Why are you always so hostile :-) Of course I made it all up LOL What a silly notion/thing to say. I've sent email to bplan about firmware and I've had no reply.
I can google a 10 year old x86 motherboard and get the BIOS updates for it. When you download the said updates it states that you may break it, of course there's always a risk. This is why they state it, most times they have an agreement you have to accept.
The firmware updates should be stored somewhere and made available, mostly for historic reasons.
Look at Video card BIOS flashing, there's a site dedicated to storing all ATI BIOSs. It's common place to flash video cards.
You can even use ATI BIOS editor to overlock at the BIOS level, PC only of course.
I've flashed many a PC motherboard, I've even saved a couple through work that wouldn't post by doing blind flashing.
At the end of the day it's the person who's flashing the hardware that's responsible for the outcome.