I did think about puting M732 thumbies on a a 10 speed system but chickened out as I will be racing that bike. I did use however Paul Thumbie adapters and Dura ace 10 speed bar end shifter to make 10 speed thumbies. The same can be done with 9 speed DA bar end shifter to make 9 speed thumbies.
To make a 9 speed disc for M732 thumbies reproducable they would need to laser cut. That way they would be perfect. It's an idea.