You know that Project Voltage collab Miku and Pokemon did? I made a pokemon sdra2 Au for fun. So here is the type(or types in Void's case) I think they would specialized in. I will explain why if I can.
Emma: Fire And Ghost type. Fire because her shitty dad used her as an Ash tray, and i honestly want her to return the favor back at the very least because she deserves to get revenge and use him as an Ash tray. Ghost because of her execution
Hajime: Dark and Fighting. Dark because he was a delinquent and he was the first to kill. Fighting because he is the Ultimate Boxer
Hibiki: Fairy type. She's the Ultimate Singer and it seems fitting for her to have fairy type.
Iroha: Posion and Fairy Type. Fairy type because she is childish in game, and she was locked up in her own home like a princess in a fairytale. Posion type because of trial 5 and most poisonous/Venomous things in life are either very colorful or people had died from it before of the dyes in the past, also because she is a painter.
Kanade: Ghost Type. She killed people and she is the Ultimate Guitarist so I thought it was the most fitting.
Kokoro: Ice type: Her personality and death. Moving on
Mikado: Electric and Fire Type. Fire type because he often use fire magic and Electric type because he is an AI.
Nikei: Dragon Type and Dark Type. Dark type because he betrayed Void and to me, Void is kinda like an Cult to me and you can't tell me otherwise. Especially when they were called The children of Usturo. That sounds an Cult to me. Dragon type because he was the original leader and because it just fits him in my opinion.
Setsuka: Fighting Type. It's basically the 'Justice' type in pokemon and she was a Detective after the Tragedy.
Shinji: Water type. Just because he is the Ultimate Firefighter and he was burned alive. Water types would be the most useful for firefighters.
Syobai: Dark Type. He is the Ultimate Broker and That's the only reason other than I thought it would fit.
Sora: Steel Type. I thought it was the most fitting type out of them all. Though I did wanted to give her both water and normal type but decided that only Void should use two types. I also didn't think Electric type would be very fitting for her so steel seems like the perfect middle ground in this situation.
Teruya: Grass Type. He's the former Ultimate Merchant and I think Grass Type would be the most useful type for a Merchant. You can make plenty of things with plants as well as sell them.
Yoruko: Poison Type. Two words. Alcohol Poisoning. Her execution was her drowning in alcohol basically, so I think it fits.
Yuki: Normal Type. Ultimate Lucky Students are probably always going to be normal type to me and It's the most fitting type I can think of.
Yuri: Psychic Type. A lot of space related pokemon are Psychic Type and he is the Ultimate Spaceman.
Thank you for listening to me here's some bonus very rough sketch of Pokemon Trainer Iroha and Emma. Iroha's pokemon is Poipole and Klefki and Emma's is Hisuian Zoroark and Blacephalon: