There are asbolutely “lite” local systems that could do things like make particular NPC behavior in certain environments far more interesting and unpredictable, without harming performance, which is what everyone I’ve ever played games with would want over the same scripted paths and triggered behaviors.

I don’t think OP is asking for AI implementation that gives you an alternate path into the enemy base by romancing one of the guards and having a life together before you steal their keys off the dresser one morning and then then break into the facility as they send you child-support notices. We’re talking about maybe enemies have more options than crouching behind a red barrel or resuming their patrol when the shooting stops.