If there is no actual physics involved, and you have set animations for what happens when hit, you can have multiple colliders parented to the object in motion. Then use a trigger collider that fires the FSM for changing the animations. You can also apply physics in the same state if you wish for them.
Edit: You would want a global transition from that trigger hitting a tagged non trigger collider on the opponent. That way it goes STRAIGHT to that FSM.
At least it's one way of doing it.