Interesting analysis.. . I agree with a lot of it.
I might add Roland EA7 is loaded with styles for every region. Too bad it may well be the last decent Roland arranger. It has the most and best, to me, simple country/western styles, except for waltz.
I've not had much trouble finding the styles I need for Korg, although their recent emphasis has been on genres of music that this old man doesn't much get into.
I've had some success converting midi files to styles on the 4X.