Hi,
Photon has a "group" feature, but I never worked with it, your solution would be what I would go to myself:
-- each player has an Fsm where you have a variable "Group Id"
-- send an RPC to all, but only the one of that group will respond.
I have another technic however, that could be good too.
If your groups are known during editing, like enemies, allies, or team A, team B, you could have hardcoded events like "TEAM A / DO THIS", "TEAM B / DO THIS", and each player when instanciated would either have fsm enable disabled based on their group so that they only respond to their events, or you could attach to the player as a child a gameobject with the right set of fsms for that particular team.
If you want to explore the photon group feature, let me know, I am willing to investigate this further and provide proper access within the PlayMaker custom actions.
Bye,
Jean