Motionfx
Does it work with rigged meshes?
Not yet. However, in the next update (Version 2.0), full rigged mesh and armature support will be added.
Why is it slow? Will it get faster?
Right now, the algorithm is slow because the blender API doesn't allow you to get or set multiple vertex positions at once, so it has to be done individually. In a future update (likely Version 3.0), all functions will be be optimized with either C or Rust, and that should at least double the speed.