While Dark is the "evil" type, I wouldn't mind a literal Light type that's not an opposite of Dark but instead deals with actual light, like Ampharos and Volbeat. Sound type also wouldn't be that bad.
The type I want the most is Space. It's considered part of Psychic, but space has absolutely nothing to do with the mind or magic. It's just that way because GF decided to arbitrarily group it under Psychic. Like Fairy-ish stuff was Normal before Fairy was introduced.
Alright, here's what I would do for Space/Cosmic.
Pokémon retyped:
Cleffa, Clefairy and Clefable: Normal > Fairy > Fairy/Space
Staryu: Water > Water/Space
Starmie: Water/Psychic > Water/Space
Solrock: Rock/Psychic > Rock/Space
Lunatone: Rock/Psychic > Rock/Space
Deoxys: Psychic > Psychic/Space
Elgyem and Beheeyem: Psychic > Psychic/Space
Minior: Rock/Flying > Rock/Space
Cosmog and Cosmoem: Psychic > Psychic/Space
Celesteela: Steel/Flying > Steel/Space
Necrozma (Normal Form): Psychic > Psychic/Space
Solgaleo, Lunala, Dusk Mane, Dawn Wings, and Ultra can stay the same. Palkia too,
Don't know about moves. Cosmic Power certainly.
As for new items:
Space Gem: Boosts Space moves to 1.3x power, one use.
Spacium Z: Z-Crystal for Space moves. Space Z-Move attack is Neutron Star Collision (Black Hole Eclipse was already taken for Dark).
Space Memory: For Silvally.
Cosmic Plate: Boosts the power of Space moves to 1.2x, also for Arceus. No other Space-boosting item is needed, because like Fairy's Pixie Plate, Plates have already been introduced at this point.
As for matchups, I'd find some excuse to have Ice resist it.
/fanfic
