I only tried changing SkillEffects and/or PotionEffects, copy original effect, change resistances on CC spell like Fear, next i renamed Fear to XXFear and replaced original Fear (in spell properties) to XXFear, its something like new spell but not exactly new. Image below will show where i made changes (not all at once but with random combinations).
In game version 3.0.146.969 tests showing only icons like Terrified but no true effect, btw before last patch this method worked without problems, targets with full physical and/or magical armors were terrified.