It just occurred to me that there is another alternative, namely:

Leave the Styles unchanged
Use NI Bandstand for non-drum channels
Load up Soundfont XG Drum Kits in a separate VST utilizing something like LiveSynth Pro or SynthFont, etc.

This would work but you would need to know on which channels the drums are located for each to the Yamaha styles....a pain. and block those channels from going to Bandstand. Everything is possible and so is this. You might take a moderate hit in quality of the drum kits but the overall result may still be better.