I think that an upper back muscle added to the Tori model would be cool and more maneuverable, because as of now, your torso is forced to stay straight up at all times, and that is fairly unrealistic. I don't know what specific muscle it would be called, but I think it would add more opportunity for power in arm movement, and as of right now kicks are very popular, so it might add some diversity to Judo/Aikido.

I also would like 4-directional hand movement, but that has less of an effect as something like the upper back.

Thank you!