Yep it would be good if there was a slider instead of 3 difficulty options.
If the AI was tweaked as I described so they would instinctively sprint between cover to find positions to scout / shoot enemies instead of shooting out in the open this would probably make them quite a lot better opponents.
Better still would be if there were a bunch sliders like follows -
AI aggression - how much an AI will seek you out if you engage them
AI awareness - how easily they will become aware of you if you are within their field of view (also the distance they will engage you if you haven't shot at them) / how quickly they will pin point you via sound / how easily you can be hidden in vegetation
AI player health awareness - how much the AI will take notice of the players health in determining whether to continue a firefight / run after a player or whether the AI should regenerate health / run away. ie - if the AI has had 4 successful hits with a certain gun then the AI will assume the players health is below 20% for a minimum of 7 seconds, whilst the AI's health is 80% so they will run after the player who is trying to hide.
If the slider was all the way down the AI won't take this into consideration and the other sliders take priority - ie aggression.
If the slider is halfway then the aggression / cautiousness / other sliders are equally important as the AI vs player health in determining whether to continue a firefight.
If the slider is all the way up then the AI vs player health is the only determining factor until 7 seconds have passed from the last hit and it is assumed the players health has begun to regenerate. When it is assumed the players health is regenerating the other sliders take priority.
AI cover cautiousness - how much an AI will try to get to a covered position before or if engaging in a firefight.
AI cautiousness - how much an AI will try to run away from a firefight they are engaged in order to regenerate health / get out of the firefight so they can continue to the objective.
AI light vehicle cautiousness - how much an AI will try to avoid or engage enemies in light vehicles who can be shot - ie LATV4, hovercraft, other vehicles you can be shot in - ie doesn't require rocket to kill people inside.
AI heavy vehicle cautiousness - how much an AI will try to avoid or engage enemies in heavy vehicles - ie Tanks, MAV, anything that requires explosives to kill the people inside.
AI accuracy under 100m - how accurate the AI are within a 100m distance
AI accuracy over 100m - how accurate the AI are over a 100m distance
AI accuracy rockets against infantry / ground vehicles - how accurate the AI are with rockets against infantry / ground vehicles.
AI accuracy rockets against air vehicles - how accurate the AI are with rockets against helicopters / planes
AI squad tactics - how much the AI tries to stay together as a squad
AI request responsiveness - how much the AI tries to fulfil a request - ie revive, ammo
AI transport request responsiveness - much the AI will go out of their way to pickup a player when a player requests a ride.
AI tactical planning - how direct a path the AI will take to each objective - ie how far will they alter their path to avoid engaging with enemies.
AI personality randomiser - each AI will vary from the sliders within a set tolerance - ie if you set the randomiser to 0.2 then the AI aggression will be within 20% more or 20% less than the slider value with different values for each AI.