Finally got a fix for this uploaded in the first post - I've named the file as beta 6.1.1 to make it obvious that it's the fixed version, but in terms of content it's 100% identical to 6.1, just with the Japanese Arcade disc rebuilt to actually work this time. Even the GT mode disc is unchanged, so only the Arcade disc needs to be re-patched, and there's no incompatibility with saves from 6 or 6.1.I don't know if anyone has had the same issue, but using the latest complete version, the japanese arcade disc shows a black screen/hangs after the intro cinematic instead of the menu. The american arcade disc works fine.
The downloads for all of the other regions have not changed either, so this is only relevant to the 500 or so people who have downloaded the Japanese version of the mod since the beta 6 release.
In beta 7 I'll probably borrow some of Silent's patches in order to get the Japanese Arcade disc to run on the same version of the code as the re-released GT Mode disc, which will eliminate the minor differences that the Arcade disc has to the other regions in terms of file structure due to being so old a build, and comprehensively avoid the chance of Arcade-specific issues like this in future.