Quote - Hmmm, I suppose one could also use magnets to flex muscle groups. Do magnets work across material zones?

They can, yes.

Quote - considering other new features, could the falloff zones or the shape of the joint capsule distort the mesh to simulate muscle flexing/relaxing?

Possibly.

Of more interest to me ... will the multiple-falloff-zone and capsule-falloff-zone options also be available on magnets?