Hi,
no, you can't do that, as I said, the only option is to wrap it in your own class, and yes, it's therefore tricky to apply something to all actions.
The problem with this is the conflict between several tools willing to each change the FsmXXX variables.
However, maybe you should contact Alex Chouls directly ( or if you are part of the beta, open a thread on this), because I certainly understand where you are coming from, I too would like to do such thing, and not just in PlayMaker but overal inside Unity.
Bye,
Jean