What's wrong with using a parameter that is already present for controlling a behaviour that sounds exactly like the kind of thing it is meant to represent?
Nothing at all. IMO it would make sense, if this stand-off thing ever gets implemented, to use "courage" to influence how close the AI is willing to let the enemy get before retreating. I did this with the stalemate detection stuff: how long an AI pilot is willing to endure a "stalemate" situation before breaking is influenced by the patience attribute, which was previously actually not used for anything.
There's also nothing wrong with making it a completely new AI class parameter, maximizing flexibility.