So I got this idea in Armored Core for Answer wherein there is an Hard Difficulty . The difference is there will be a different event or sometimes fill up missing parts of your gameplay and of course all weapons are double damage even their health (though you wouldn't even realize it)
So my idea is in the end of the game Genocide Mode will be unlock set in the most highest difficulty, All enemy deal double damage, have double health, smarter AI and sometimes makes a different event in the mission example in level 2 instead of the elevator being activated it won't.
So A.I behavior so you know that AI only knows Run, Jump and duck but no other movements other done that and sometimes recklessly charge towards the enemy well how about more. You could set it in Level Editor
Default, Investigate, Follower player and do nothings is already here.
Reckless- Will charge towards to enemy ignoring its defensive behavior
Coward- Will try to keep away from gun fights and run anywhere in map
Flanker- Will try to attack you in different directions other than the its enemy location
Suppresive- When an enemy is found will spray bullets in the enemy direction
Medic- Will revive ally no matter what (Deactivated and restored to default if Defib by AI is deactivated)
Reckless Medic- Will try to revive ally even if there are gunfires happening
Defensive- Will try to duck more often and jump if needed while keeping its distance away from the player
Random- Choose a random Behavior