Gamefreak has summoned you and wants you to give every fully evolved monotype starter a second typing. What do you give them?

Blastoise: Water/Steel

Meganium: Grass/Fairy
Typhlosion: Fire/Ground
Feraligatr: Water/Dark

Serperior: Grass/Psychic This would probably make it even more shit but I can't think of another type that fits
Samurott: Water/Fighting


Bonus points for typings that fit and also vastly improve the Pokemon.