The AI all depends on what you want out of your enemies. There is no "one" AI for any game. Each enemy's AI is dependant on their purpose. Find the purpose you want to have for you enemies, then find the script to match it (as close as possible).
Scripts are saved as ".fpi" files, not fpe. ".fpe" files are for entity declarations.
The one and only,
Those who live in the past, are destined to insanity. Those who live only for the future, will be slaves to their ambitions.
Those who live in the moment... only they, are truly happy.