That's such a great project! But I'd love to see a proper VST with it, that allows voice mixing. The power of organs lays in the analog voice mixing (not simple on off, and not one voice exclusively)
https://www.hauptwerk.com/ is paid software but has a few Schnitger organs, although not the one shown off here.
There's also Sweelinq (https://sweelinq.com; subscription model), and Grand Orgue (free, but cumbersome; only a few worthwhile sample-sets), and there are some instruments for Kontakt.