With every new Pokemon generation, fans begin to speculate what new features will be added to the series. These new features include ways to interact with your partner Pokemon or ways to interact with other players. What excites fans the most, however, are features that affect the franchise's creativity, like new Pokemon types.
In the Pokemon franchise, types are categories of Pokemon that determine their moves and abilities. One potential type that hasn't been included yet is the "Light" type, as Pokemon who would fit this typing usually fall under Fire, Fairy, or Psychic-typing. However, these Pokemon would be the best choices to become Light-types if it ever was added to the series.
12 Chinchou / Lantern
This Water/Electric-type duo originated in Pokemon Gold & Silver, the series' second generation. They're an easy update, just by exchanging their secondary Electric-typing for the new Light-typing. This would fit Lantern since Pokedex entries say that the anglerfish-inspired Pokemon illuminates the deep sea for over three miles.
In terms of its moveset, it stands to reason that Lantern would probably lose most of its Electric-type moves in favor of new Light-type moves. Lantern and Chinchou would probably also lose the ability Volt Absorb, while easily keeping the ability Illuminate.
11 Sunkern / Sunflora
Also from Gen 2, Sunkern and Sunflora are based on a sunflower seed and a sunflower, respectively. Therefore, it's easy to see how they could be changed from pure Grass-types to a combined Grass/Light-type evolutionary duo. Furthermore, Sunkern even evolves into Sunflora using an item called the Sun Stone.
Since Sunflora's Pokedex entries record it using sunlight to fuel its energy, perhaps it could use a change in Abilities as well. If a Grass/Light-type Sunflora was given the Ability Sunny Day, it would be able to use Solar Beam without having to charge, which would certainly fit its Pokedex descriptions.
10 Ho-Oh
This Legendary Pokemon was first revealed at the very beginning of the Pokemon anime. Dubbed the "Rainbow Pokemon", Ho-Oh's feathers glow seven different colors, and it appears before a Trainer to bring eternal happiness. These reasons make it an obvious choice for Light-typing.
Ho-Oh's current typing is Fire/Flying, meaning the Light-typing would probably replace Fire as Ho-Oh's primary type. This probably works out for the better, since it doesn't make much sense for the rainbow-centric Ho-Oh to be Fire-type at all. However, it could cost Ho-Oh some powerful Fire-type moves, like Fire Blast or Sacred Fire.
9 Volbeat & Illumise
These pure Bug-type Pokemon first appeared in the third generation games, Pokemon Ruby & Sapphire. While these Pokemon have no evolutionary connection to each other, they are able to produce eggs that contain either one of the two. Due to their firefly-inspired design, it would be perfect if these two were both Bug/Light-type.
A possible new type could also boost Volbeat and Illumise's current standing in the competitive meta. As of right now, the Pokemon have moveset coverage for Bug, Psychic, Normal, and Fairy-type attacks. Depending on Light-type's strengths, it could make these two threats in battle. However, they may be held back by their poor stats.
8 Cresselia
Cresselia is a Legendary Pokemon found wandering the Sinnoh region in Pokemon Diamond & Pearl. Its design is based on the crescent moon, with its Pokedex entries describing its glimmering beauty in the moonlight. Curiously, Cresselia is a pure Psychic-type, despite none of its abilities relating to telekinesis or mind-reading.
With this in mind, it would make the most sense if Cresselia was a pure Light-type Pokemon. This would also distinguish it from its counterpart, the pure Dark-type Darkrai. Cresselia would also benefit if certain moves, like the Fairy-type Moonlight or the Ice-type Aurora Beam, also became Light-type moves as well.
7 Lilligant
Lilligant has had some recent attention from Game Freak, as it was given an alternate Grass/Fighting-type form in Pokemon Legends: Arceus. Its original form, which first appeared in the fifth generation's Pokemon Black & White, remains pure Grass-type, though it could easily be argued that Lilligant could be a combined Grass/Light-type.
Similar to Sunkern and Sunflora, Petilil evolves into Lilligant when it is given a Sun Stone. It makes sense for this flower Pokemon to be Light-type, as it relates to its Pokedex entries, which claim Lilligant is more powerful the more fully-bloomed it is. This would also make it more distinct from its Hisuian counterpart.
6 Zoroark
This Dark-type Pokemon, along with its pre-evolution Zorua, was the first Pokemon revealed for the series' fifth generation. It also starred in the animated movie Zoroark: Master of Illusions. As the film's title suggests, Zoroark is capable of creating illusions to trick Trainers and Pokemon in order to keep it and its pack safe.
While not directly connected to the sun or sources of light, it could be argued that illusions are a different kind of light that would warrant Zoroark to become a dual Dark/Light-type. This could also add some variety to Zoroark's learned moveset, which is currently mostly occupied with Dark-type moves.
5 Heliolisk
As another recipient of a Sun Stone evolution, Heliolisk is one of the most obvious changes to Light-typing. Like its pre-evolution, Helioptile, this Pokemon is currently Electric/Normal, which is an interesting type combination. It would make sense if Helioptile's evolution into Heliolisk changed its secondary Normal-typing to Light.
Heliolisk could also be one of the flagship Pokemon to promote the new Light-typing like Gardevoir and Jigglypuff were for Fairy-type in the sixth generation. According to Pokedex entries, Heliolisk basks in the sun and stores enough energy to power skyscrapers with electricity, making it perfect for Electric/Light-typing.
4 Xerneas
This pure Fairy-type is one of the flagship Legendary Pokemon in Pokemon X & Y. Since this generation introduced the Fairy-type, it makes sense that Xerneas was used as a way to draw attention to this new type. Xerneas could do the same for Light-type since a dual Fairy/Light-typing would fit it well.
Like Ho-Oh, Xerneas is remarkable for its glimmering, rainbow antlers. However, it also has an alternate Neutral Form that drains the Pokemon of its color. Perhaps Xerneas could be re-interpreted to change between these two forms, with the Neutral Form being pure Fairy-type, and the Active Form gaining Light-type.
3 Lycanroc Midday Form
Lycanroc was introduced in Pokemon Sun & Moonwith two forms that evolve from Rockruff. Its Midday form, which prioritizes speed, evolves during the day, while its Midnight form, which prioritizes defense, evolves at night. Midday Lycanroc could therefore easily change to a dual Rock/Light-type.
However, it wouldn't be fair to leave Midnight-form Lycanroc unchanged, so that form could arguably become Rock/Dark-type as a counter to Midday's Rock/Light-typing. As a bonus, Lycanroc's Dusk form, which was only available via Event, can remain pure-Rock as an in-between of the two wolf Pokemon.
2 Solgaleo
This Pokemon is one of the easiest candidates for Light-typing as the mascot for Pokemon Sun. Currently, Solgaleo is Psychic/Steel-type, which means that its sun-inspired aspects are currently unrepresented. To keep it parallel with its fellow Psychic/Ghost flagship Lunala, Solgaleo could become Psychic/Light-type.
Solgaleo also benefits from an already diverse learned moveset, including Solar Beam, Wild Charge, and Flare Blitz. It could very well keep some of its best Steel-type moves, like Flash Cannon and Sunsteel Strike, while also gaining new Light-type moves to take advantage of STAB attacks.
1 Ursaluna
Ursaluna was recently introduced in Pokemon Legends: Arceus as a Ground/Normal-type evolution of Ursaring. In the game, Ursaluna evolves when Ursaring is exposed to a Peat Block during a full moon. Due to the mysterious connection this Pokemon has with the moon, perhaps Ursaluna could be Ground/Light-type.
Pokemon Legends: Arceus also takes place in an ancient version of the Sinnoh region. This means that an Ursaluna appearing in a main series game could be vastly different from the one players meet in the Hisui region. Perhaps this alternate version of Ursaluna could have more of a connection to the moon, warranting a Light-typing.