>>24527730I'd say for possible mega retypes:
Poison/Water for Muk (water pollution)
Poison/Fire for Weezing (learns fire moves, and goes well with exploding mine and exploding gases)
Poison/Steel for Garbodor (industrial pollution)
All of them are novel types, and if they all gained a poison recovery move, they wouldn't miss black sludge. Gen 7 poison gen when?