In the future, consider revisiting how joints, positions and layer types interact

[qoh]

It should be possible to do things like setting the parent of an arbitrary line handle, light, particle emitter, etc. to a joint and positioning it relative to it. Animating the figure owning that joint would then also animate those children. Generally this should be the same overall joint parenting system for everything, including figures (and you should be able to parent a figure to something that isn't a figure).