This one's a tough one...
Well. It's been a year of me trying to unbrick my poor brick and I have reached the end of my options I think.
Let me start with what I have:
wii from original release (this thing is old) running 4.2U that boots to black screen. Nothing else.
bootmii v1.3 as boot 2
complete software backups of at crash, and before crash.
Before I synced the wiimotes to another console, they could be used to power it on.
Then, what I have tried (in order):
restoremii via bootmii of before crash
region/ settings.txt fixes
savemiifrii (menu version displays and stays there until I put in a disc or press a button. Dunno what to do with that)
reseating bluetooth and wifi boards
and finally, my thoughts on what could be the problem (in order):
Bad wifi board (this thing doesn't look like any I have ever seen and looks like someone thermal pasted it to the motherboard case)
bad bluetooth board
Now if it is the motherboard, I think I'll just buy a new wii.
While I won't be able to bootmii as boot2, It'll give me an excuse to play through Okami again.