100% agree with your thoughts on overwriting a factory sound - Exactly why we haven't tried the earlier suggestion. Even though this video was done on SD40, it works the same on SD90 regarding user voices..
https://youtu.be/TuyCHsfSrSEThe catch is accessing the user voices in a style. That seems to be the missing piece for what you would like to do.
Yes, thats a lovely interface..
But its kind of confusing to call this voices too
As they are actually a combination of 4 voices.
Korg pa4x calls these keyboardsets
What Ketron needs to do is add (most of)the 6 pages of edditing parameters for ever style and midifile part... and with an option to save them..