if you use the same FSM a lot then a template is indeed what you'd want to use.
And no, unfortunately PlayMaker has very little to offer in sense of extensibility. Most of the interesting parts are in the .dll, and unless you decompiled them with a decompiler like *cough*
http://ilspy.net/*cough*, you won't be able to change that. Since wof course you will not use any such techniques because you know that would be illegal, let's just say you try around until you find the right class structure and functions quite by accident, then I guess it should be possible to extend the system in a separate plugin, not sure though as I've not yet had the time to
look try combinations to find the right functions.
(I hope this post does not violate any forum or license rules. If it does, or if it is rude to the developers then of course I'll cut it short.)