Tekken 5 includes the ability to play the arcade versions of Tekken 1, 2, and 3

Tekken 1 and 2 run on System 11 arcade hardware
Tekken 3 runs on System 12 hardware.

System 11 hardware is almost identical to ps1 hardware, and System 12 hardware is System 11 hardware with more memory.

The execution of these games from within tekken 5 even includes access to the arcade rom test menu to set things like number of rounds and round time limit. There is quite a lack of anti-aliasing on all three games, so I wonder if they might be running on emulated arcade hardware rather than recompiled to run on the ps2.

Perhaps it might be something like bbnav?

Anyway, I'm not nearly talented enough to investigate this further, but I'd like to think that it at least merits unpacking the TK5DATAx.BIN files to find whether the old game portion of them contains roms, or just models and other game data.

It could be a dead end, but then again it could be a step toward booting ps1 games off the HD.