Brief update: Bootloader now fetches decrypted kernels via IO, not AHCI. This fixes USB storage devices, including the internal HDD (there's a very long story behind this issue). There has been significant performance improvements resulting in smooth framerates. Texture loading issues are solved, which fixes some artifacts. We have added support for PUPMGR functions, though decryption is still pending pending, hence the error in the end. Several SAMU high-level emulation issues have been fixed. Finally, we added the possibility of reinstalling firmware via virtual mass-storage USB devices.
Hats off to everyone involved (this wouldn't have been possible without the contributions from @glamhoth and @jarves), and special thanks to all supporters. :-)