What do you mean by “third level players” here? You call “second-level strategy” already modeling other players, but
you can model them as third level players and not have to treat them as equals.
… makes me think you maybe meant first-level players?
Anyway, I would model most of my opponents as what you call first-level strategy, with some varying parameters (and extra randomness). And possibly include as part of the population whichever more exotic strategies can systematically beat (various mixes of) those.
What do you mean by “third level players” here? You call “second-level strategy” already modeling other players, but
… makes me think you maybe meant first-level players?
Anyway, I would model most of my opponents as what you call first-level strategy, with some varying parameters (and extra randomness). And possibly include as part of the population whichever more exotic strategies can systematically beat (various mixes of) those.