Ahh the good old "conversation is a state machine" pitfall. Even linguists I work with do that sometimes, I guess it's how the simple models that we're taught with work.

Wanna have the simplest parser? Finite State Automaton to the rescue! So people automatically assume that a the simplest approach yo conversation is also something like a finite state machine.

Here's the thing. The only reasonable FSA would be a clique.

You can always move between nodes.

A much more feasible approach is the "actions competing for repelevance" one. Where you have global state manipulated by actions, and all the actions generate a "appiccability score" for the given user input. The system then chooses the most appropriate action, and it does it's thing. And on the next user input the cycle repeats.