Motion mixing and transition blending

I would like to request non-linear animation for jME. This could be done for both skeletal animation and morphing meshes.

Motion mixing: Blend two separate animations together to get a new one. For example, one animation of a person walking + person waving = person walking and waving.

Track blending: Smoothly transition from one animation to the next; i.e. after jumping, transition to a walk animation smoothly.

I’m not sure exactly how this would be programmed, but it seems to me if you can do motion mixing, track blending should be a cinch. But strangely, many game engines only do track blending. I never understand this, since motion mixing greatly cuts down the number of animations you have to do by hand in the 3d authoring program.