I've tried this, several times. But it doesn't work properly. The "new" renamed style will save and it can be selected, (manually from the pulldown menu).
But when selected, it always plays the old instruments that were "deleted".

Also, the style picker window doesn't update with the the "new" style, upon rebuild. The Renamed style can't be found that way.

I must admit that I'm miffed! PG has said that the Windows folks can do it, but that we Mac users can't. Get with it, PG!!!