Ok, so long story short, I went to square one and built my own EFI from scratch using the DEBUG channel. Using this, I was able to boot the Catalina installer and install it on an NVMe SSD.
This is a fairly barebones EFI, I've attached it here for reference.
One question
@AudioGod, I noticed you do not have the NVMEFix or AppleMCEReporterDisabler kexts in your EFI, is there a particular reason or conflict for that? I included them here per the Dortania guide and was able to successfully boot.
I then tried to boot to the installed Mac partition using the AudioGod EFI, with the only change being to update my SMBIOS details that I successfully installed with previously. It stalls out about 75% of the way through the boot sequence.
I'm wondering now if it's possible to troubleshoot my way through this by somehow merging the two EFIs. I've at least eliminated the notion that it is an installer issue at this point, which is a step in the right direction.