Comment about vertex attribute: It seems to me like it is using just an attribute, which you can use for a Cycles shader for example. I think it would be better if the user could select a vertex color layer for that so the effect can also be previewed in non-rendered viewport. And using weight layers (for absolute force) could make this even useful for some nice motion graphics effects.

2 problems with vertex color layers:

• All kinds of assumptions can be made in other parts of the code about this, in particular clamping, color corrections and other stuff can happen. The vector value (and related values) is NOT actually a color though, so color-related processing does not make any sense.
• vertex colors are stored as 4 uchar values (0..255), so trying to store a vector will not work for float values.