I compiled the IOGraphicsFamily.kext yesterday and added debug output to located the root cause of missing and deformed Apple logos during the first, second and third boot stages, and I think to have located the problem.
I’m now working on a solution without adding workarounds like patching the kext to simulate verbose boot ups et all. However. I am still very busy with something else so you will need to wait for me having the time for it. Will report back as soon as I have more news for you. Hopefully sometime next week.