So mirror armor reflects stat lowering effects and I know if he got overheat it will not give them an -2 sp.attack but! That means his stats can't be lowered cause of mirror armor so if you give him an eject pack any stat lowering move he uses that's a pivot move without abilities like intimidate!
Does he have ANY moves that could switch him out paired with an item? (Scarlet)
*I tagged it future sensitive cause his moveset could change right?