Fate/Grand Order Summer Servants I Would Like to be Added.

4 or 5 Star

Berserker, Caster

She already had a swimsuit in Hollow Ataraxia

5 Star

Caster, Ruler

She already had a swimsuit in Hollow Ataraxia, she's a Ruler because Summer Kama is Avenger.

5 Star

Caster, Foreigner, Berserker

She had a swimsuit in Witch on the Holy Night, Berserker is there due to her personality and Foreigner is their because Foreigner Servants can't change their class by normal means.

5 Star

Moon Cancer

Her "mother" and "sisters" all have swimsuits already, she's a Moon Cancer due to her existence being a threat to the Moon Cell.

4 or 5 Star

Rider, Berserker, Ruler

She already seems to have a swimsuit underneath her clothes, she's Rider due to how she traveled around the world, Berserker due to her usual NP, and Ruler due to achieving enlightenment.

5 Star

Rider, Pretender, Alter Ego

Who wouldn't want that body in a swimsuit, she's Assassin because I imagine her attack animations with her riding a magic carpet, Pretender and Alter Ego for being a storybook character.

4 or 5 Star

Assassin, Pretender

She already appears in multiple summer events, she's Assassin because she kills your wallet and Pretender because she's a con artist.

4 or 5 Star

Archer

She would be funny to pair with the chicken enemies, she's Archer because I can imangine an attack where she launches Kykeon.

5 Star

Berserker, Alter Ego, Moon Cancer

She's funny and there are many of her attack animations from EXTELLA that didn't make it into FGO, she's Berserker due to her real world story, Alter Ego due to her just being a smaller copy made by the original, and Moon Cancer for obvious reasons if you played EXTELLA.

5 Star

Berserker

Their are lots of GUDAGUDA Servants already, what's one or two more, she's Berserker due to the physical strength she already possesses.

4 Star

Assassin, Berserker

If the above is 5 star, make her sister 4, she's Berserker for her usual fighting style and Assassin for being a walking curse of bad luck.

4 or 5 Star

Berserker, Moon Cancer

Their are almost as many version of her as Artoria, but no swimsuit unless you count Carmilla, she's Berserker due to her being summoned as one in Fate/EXTRA CCC and Moon Cancer due to her origins in the series being from Fate/EXTRA.

5 Star

Avenger

All versions of her already got a swimsuit version except this one, she's Avenger due to her non-Alter version's Summer form being Ruler.

5 Star

Beast, Alter Ego

Tiamat just got a swimsuit so let's finish the main cast of Lilim Harlot, her final boss outfit in the Arcade version also kinda looks like a swimsuit to me, she's Beast because Beasts can't change their class through normal means and Alter Ego since she was one in the Arcade version.

5 Star

Saber, Archer Pretender

The other Fae Knights have swimsuits so give her one now that she's an honorary member, she's Saber or Archer due to being a knight and already being Lancer and Pretender because her mother is the original her.