I’m picking only schoolchildren, both from Twilight’s school and Ponyville elementary.
Hajime Hinata — Pipsqueak
Talentless (yet) and a dork. (shrugs)
Chiaki Nanami — Button Mash
Duh.
Sonia Nevermind — Silverstream
A naive foreigner with a positive attitude. Plus, she’s totally shippable with Gallus.
Akane Owari — Yona
Eats a lot, punches stuff a lot. Loud and energetic.
Hiyoko Saionji — Babs Seed
One of the least fitting choices on the list, but, eh, can’t win it all I suppose. However, she’s got a capacity to be a bully and self-esteem issues.
Gundham Tanaka — Gallus
Brooding boy with a heart of gold. All he needs now is a hamster army.
Kazuichi Soda — Snails
Second thirsty after Snips. Looks like a punk too.
Mahiru Koizumi — Smolder
«You’re a dragon, right? Then act like it!»
Teruteru Hanamura — Snips
Complexion fits, and I can easily imagine Snails to be a little bit too thirsty.
Nagito Komaeda — Sandbar
Messy hair, dorky, probably gay. «I want your friendships to shine!»
Nekomaru Nidai — Applebloom
Strong, courageous, and she even trains other people too as a cutie mark crusader.
Ibuki Mioda — Sweetie Belle
Basically, music connection.
Peko Pekoyama — Scoots
Possess a fighting spirit and fits well with Rumble being Fuyuhiko. At least in my head.
Mikan Tsumiki — Twist
A soft-spoken punching bag.
Fuyuhiko Kuzuryu — Rumble
Grumpy, uncooperative, wants to stand on his own without his family.
The Ultimate Impostor as Byakuya Togami — Ocellus as Diamond Tiara
Obvious choices, both for the impostor and for Byakuya. During the time in school Ocellus impersonated Featherweight (Ryota).