I was wrong about the dm-raid45 bit being the cause. I just rebooted on the repacked image and it behaved in the same broken way as before.
I will go dissect an old working image and try to see what the difference is.
This is just a matter that the raid456 module isn't being loaded when it should be...
Why it is not being loaded, I don't know yet. Jesse Molina wrote:
The initramfs file /conf/modules says "dm-raid45", but I suspect it should say "dm-raid456". I suspect this typo is causing the module to not be loaded, causing boot to fail, but I have not verified this yet. I will repack it and reboot on it in a few minutes here.