You can extend the animation bridge rather than adding new states.
If you use a 3D bridge this is already there (as you have state and facing direction), but its not hard to make some adpations to the 2D bridge to send custom strings when certain combinations are met (e.g. see the 2D Bridge with transitions).
I am thinking of doing away with AnimationState all together, and replacing with strings. hard to do this in a backwards compatible way though.