I don't have any slightest idea about the Xcom AI.. and as i see there is no AI file to edit.
So if there is people who knows how the AI works, please enlighten me. I want to edit the alien weapon stats with ranges and hit chances and even damage dropoffs.. What does AI care when it's shooting?
LOTS of things.
Does it check for a hit chance limit?
Yes, indirectly, based on distance.
Additionally, in OXCE+ only, there is a true hit chance limit... but it doesn't influence the "AI decision"... only prevents the AI to waste ammo on hopeless shots if it already decided to shoot and increases the odds for reaction fire later.
Does it calculate the possibility of killing the target?
Yes, it considers "how much" damage it can do, e.g. if it can grenade many people it will go for it instead of shooting.
But it doesn't calculate exact damage, ever.
Weapon's power (not damage to target) is considered on several places too... for example if to use melee or ranged weapon if you have both.
For example, at Xenonauts, the AI got an acceptable hit chance limit before hit fires, like the enemy goes near you to get that chance or run out to safety. So if you give a poor acc weapon to aliens, they do not attack you, or rush you without firing until they hug you (something you don't want to see). Another example is, if the enemy thinks that, his fire power is not enough to kill, it just don't go aggressive too and go hiding or near to his other fellas.
Xenonauts didn't have to be compatible with anything.
OpenXcom tries to mimic the original game AI as much as possible... which cost the devs a CRAP-TON of time and nerves...
Suggestions to "improve it" are, dare I say it, "not welcome"... at least not in vanilla.
Btw. they are also not welcome in OXCE+, because I want to keep "not knowing what AI does"... or at least not knowing what little there is I still don't know.
So if i give low acc weapons, will the Xcom aliens stop shooting?
No, not in vanilla.
In OXCE+, yes, if configured so. But as said before, it won't change their decision making... it just prevents them from firing.
What will they react to limited range weapons?
They will consider them as unlimited range (during decision process)... and (most probably, not sure about vanilla) fail to shoot.
Exception are melee weapons, they know they need to get in melee range.
Does "dropoff" work to aliens shooting too?
Yes.
Should i avoid some important things when coding alien weapons then?
Don't fuck them up. Aliens deserve a chance too!