It would be cool,if this "force_diplomacy" worked depending on some AI faction's parameters i.e. :Treasury,number of settlements,military force,number of enemies and others.The idea is that if a faction is in poor situation,it would accept your demands(Force_diplomacy works).But if the faction is strong enough,you couldn't demand anything(to prevent players from overuse it).Or switch it on only if your diplomat is "polished" or "expert". I believe something is possible via scripts/traits.Just thoughts:)