Hi,
actually the style assembly feature on the yamaha 9000pro is pretty handy for creating new styles. I also have a similar feature on the kn7000.
The only problem I found, is that a lot of the styles use the same phrases ie it uses the same bassline in 2 or 3 of the variations, so you keep dialing up the same parts.
At the moment I'm going thru the whacky process of identifying the individual style parts and cataloging them for my kn7. In short, if I'm looking for a string part, it will save me scrolling through piano's brass etc , I'll know which style parts are strings.
Hopefully will take help shorten the process of actually coming up with a worthwhile style.

best wishes
Rikki