TemplarGFX’s ACM Overhaul mod includes an revised version of one of the game’s .ini files, correcting a misspelled code reference from “teather” to “tether”, and – boom – AI that actually works.
“When a xeno is spawned, it is attached to a zone tether. This zone tells the xeno what area is its fighting space and where different exits are. In combat, a xeno will be forced to switch to a new tether (such as one behind you) so as to flank, or disperse so they aren’t so grouped up etc.,” modder James Dickinson explains on the mod’s page. “Whenever the game tried to do this, nothing happened. Now it does!”