I finally got the standard Japanese Disk controller working. This means no more CDX-2 'Brazillian' driver (which honestly served me well but was not fully compatible with some late-era games). This should get all the later big RPGs like XAK II, Fray and more running! Those late-era games often bypassed the standard BIOS and called directly into the disk controller to speed up handling and the CDX-2 controller has a different interace. Technically games on the MSX should NOT bypass the standard BIOS interface for just these kinds of compatibility issues... but reality is that 99% of the Japan game-makers market was not Brazil.
That's huge... though it once again came at a huge cost of debug effort and sanity lost.
I haven't seen any regressions on disk games with the new driver so hopefully we're good here.
Version 0.9c has been checked into my github site.
I can't figure out Lubek and MSX-MUSIC. But at least that plays with the standard PSG music.