I see problems using bump/displacement maps with dependent parameters because of material zones. Firstly, if one uses dependant parameters to simulate the flexing of the biceps on the right arm, the left arm is in the same material zone with the same maps. Therefore, the left biceps will also "flex." Unless one has different material zones for each side of the body, using this as an option will cause the maps to be applied to both sides of the body simultaneously.

Secondly, there are four material zones that make up the arm (hand, forearm, shoulder, and collar). If one changes the parameters of the bump/displacement on the shoulders, there will be a line between the material zones of the collar, the forearm, and the shoulder. To show what I mean, attach a good displacement map to a figure, and use very different values for different material zones, and you should see some lines.

It might be possible to get around this second problem with specially made displacement maps merged with a base displacement map using blender nodes. I am not good at making displacement maps so I cannot try this out, but if one made maps that only effected the biceps or triceps, and blended them with a base displacement map, dependent parameters could control the amount of blending.

With a very sophisticated blender set up, it might be possible to use dependent parameters to flex only the biceps of one arm. This would solve the first problem. Of course, one might also make figures with right and left material zones.

Hmmm, I suppose one could also use magnets to flex muscle groups. Do magnets work across material zones? considering other new features, could the falloff zones or the shape of the joint capsule distort the mesh to simulate muscle flexing/relaxing?

LMK

Probably edited for spelling, grammer, punctuation, or typos.