Hi Scott! hope you have been well mate, been a long time since chatting to you on skype!
I read the thread from 2006 where you explained about the chord sequencer. It does sound very useful but I have found a work around for this on my PSR S910 (quite sure all PSR's and Tyroses from 2000 onwards can do this).
Basically in the style sequencer you can record each style part yourself and select them NOT to respond to any chord changes you make on the keyboard while playing live.
I have recorded a very unique bass line progression using 4 chords, same with strings, epiano arppegio and strumming nylon guitar.
I can also select certain other parts in the style to be variable so they WILL change chords if I want them too...
When I then play over this style it sounds great, I have a custom bass pattern playing in the background which would never sound the way it does when just looping in normal live chord recognition mode and I can still use my left hand to change chords of other style parts in the same style all in realtime.
The other answer is purchase a Motif XS or XF
Just food for thought...
Nick