Congratulations on starting off on such an awesome project!
If you're serious about making something like FMCB, I would like you let you know that I plan to consolidate all updates to FMCB/FHDB for release v1.96 in December. As part of this, I'll also attempt to document and release parts of the source code that belongs to me, which are mainly the new OSD configuration initialization and console initialization code. Things that were originally part of FMCB will have to stay close-source.
After I was given the v1.8c source, I replaced the ESR init.irx and the code that initalizes the configuration, with my own code. The original code that initialized the console required an additional IRX (init.irx) and did extra steps (some were done by EECONF, which is board-specific). The OSD configuration initialization was originally not totally correctly implemented, from what I remember.
I also changed code to support DVD Player updates (originally, FMCB only worked with the ROM DVD player). This part is being reworked within FMCB because my current code doesn't play well with kHn's work on the DVD player, and I am interested in implementing an as authentic replica of the Sony code as possible. The general code for even supporting the ROM DVD Player was also rewritten, as I found that there is a proper way to determine the MagicGate region of slimline consoles.
By exploring the official Sony TDB Startup card and from l_Oliveira's guidance, I also trimmed the known update filenames. This also includes covering for the one and only Chinese set.
And the console would not hang if the tray is ejected. I'll do some write-up to describe how these smaller details can be achieved. If you have any questions, you can also ask me.
Finally, some of the rom0 modules are board-specific. Specifically, those that begin with X, P or T. So for compatibility with all PS2 models, you should not use them. rom0:EELOADCNF is also a board-specific IOPRP Images and there is really no need to use it for rebooting the IOP (unlike what LaunchELF and OPL did... and I guess, FMCB).
If you have intent to support the PSX, there is a need for additional work, due to the hardware and kernel being in a different operating mode at power-on.
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Regarding the unfortuate incident: please consider letting this one slide, even if it does not really get resolved. The person who is probably behind may be difficult to reason with. You will just end up feeling disappointed, angry and question why your work is for people like him... but the truth is that it is probably just him. He's got friends who will support him too, so it is hard to show him that he's doing wrong.