Weird idea I just had a little bit ago: regional variant eeveelutions. I know the idea's been suggested before, but I hope my take on it is unique enough. (I also am aware the Eevee line is already in Galar.)
Galarian Eevee
Type: Normal/Fairy (Also held by Azurill and the Igglybuff line)
Ability: Normalize/Pixilate (HA: Vital Spirit)
Description: The presence of many Fairy-types has changed Eevee's genetic structure and disposition to be even cuter.
Appearance: It now has pinkish fur and a fluffier neck tuft.
When Galarian Eevee is leveled up while holding a Soft Sand, it evolves into Galarian Vaporeon.
Galarian Vaporeon
Type: Ground/Fairy (no other Pokémon has this type combo)
Ability: Sand Force (HA: Sand Stream)
Description: Vaporeon has adapted to a calm lifestyle on sandy deserts and beaches. Its sand runs as smooth as water.
Appearance: Galarian Vaporeon is a beige in color with a dark brown spiky neck frill and a much shorter less mermaid-like tail.
When Galarian Eevee is leveled up while holding a Metal Coat, it evolves into Galarian Jolteon.
Galarian Jolteon
Type: Steel/Fairy (Mawile, Klefki, Magearna, Zacian)
Ability: Sand Force (HA: Sand Stream)
Description: Galarian Jolteon has become metallic though its electricity has dulled. It can still run blisteringly fast.
Appearance: Galarian Jolteon looks nearly robotic, with metallic spiky fur and bolt-like things on its neck.
When Galarian Eevee is leveled up while holding a Hard Stone, it evolves into Glarian Flareon.
Galarian Flareon
Type: Rock/Fairy (Carbink, Diancie)
Ability: Sand Force (HA: Sand Stream)
Description: Flareon has become much cooler and sharper. It lives in rocky cliff areas.
Appearance: Galarian Flareon is a dark brown that's still fluffy, but also has many spikes upon its sides.
When Galarian Eevee is leveled up during the night while holding a Spell Tag, it evolves into Galarian Espeon.
Galarian Espeon
Type: Ghost/Fairy (Mimikyu)
Ability: Pixilate (HA: Aftermath)
Description: Galarian Espeon has developed ghostly powers, although lost some of its intelligence in the process.
Appearance: Galarian Espeon is a spooky black and green, and boasts three tails with a ghostly energy on the ends.
When Galarian Eevee is leveled up during the day while holding a Poison Barb, it evolves into Galarian Umbreon.
Galarian Umbreon
Type: Poison/Fairy* (G-Weezing)
Ability: Pixilate (HA: Aftermath)
Description: Galarian Umbreon has become much more toxic and sinister, its own sweat droplets corroding everything they touch. However, this poison can be made into sweet-smelling fragrances.
Appearance: Galarian Umbreon is a deep purple with pink band-like markings around its legs.
Note: Its typing is a reference to the fact that Umbreon was originally intended to be a Poison-type
When Galarian Eevee is leveled up while holding a Silver Powder, it evolves into Galarian Leafeon.
Galarian Leafeon
Type: Bug/Fairy (Cutiefly line)
Ability: Swarm (HA: Heatproof)
Description: Galarian Leafeon has adapted to be a cheerful Bug-type to deal with the bug-types that formerly preyed on it.
Appearance: Galarian Leafeon is a light green all over its body, with goggle-like eyes and clearly-jointed legs.
When Galarian Eevee is leveled up while holding a Sharp Beak, it evolves into Galarian Glaceon.
Galarian Glaceon
Type: Flying/Fairy (Togepi line)
Ability: Gale Wings (HA: Heatproof)
Description: Galarian Glaceon has adapted to warm high-altitude environments and gained the ability to fly.
Appearance: Galarian Glaceon still retains its general coloration but has new wing-like limbs and a more stream-lined appearance. Its tail also appears feathery.
When Galarian Eevee is leveled up while holding a Dragon Fang, it evolves into Galarian Sylveon.
Galarian Sylveon
Type: Dragon/Fairy* (Mega-Altaria)
Ability: Dragonate* (HA: Thick Fat)
Description: Galarian Sylveon is still friendly towards its allies, but is now incredibly hostile towards its enemies.
Appearance: Galarian Sylveon has a reddish-pink and blue color-scheme with no white (as well as spikes), and its ribbons are now replaced with draconic whiskers.
Note: G-Sylveon's tying is a reference to the fact that so many thought it would have a Dragon-type counterpart.
Note: Dragonate is a new ability which is basically a Dragon-type Pixilate
Galarian Eevee has two new eeveelutions: Scuffeon and Baseon, which it can evolve into if leveled up holding a Black Belt or Silk Scarf respectively.
Scuffeon
Type: Fighting/Fairy (unused type-combo)
Ability: Scrappy (HA: Defiant)
Description: Scuffeon uses many graceful styles of fighting to defeat its enemies with ease.
Appearance: Scuffeon is a reddish-pink in coloration, with bandage-like markings near its paws.
Baseon
Type: Normal/Fairy (Azurill, Igglybuff line)
Ability: Normalize (HA: Stamina)
Description: Baseon is said to be the perfect Eeveelution, as it incorporates the traits of all other evolutions. However, its DNA has stabilized and it is fully locked into this form.
Appearance: Baseon is a spiky/fluffy bigger Eevee, though with longer legs. It also has various traits of the other eeveelutions, like markings on its lower legs resembling those of Umbreon and Scuffeon, or its neck ribbons being like Sylveon's.