So since this takes place around the same time as Pokemon Legends: Arceus, their Pokéballs would have to be the same. Let's start by building the teams, then we will go off from there.

WE ARE INCLUDING ALL POKEMON THAT HAVE BEEN INTRODUCED AS OF SEPTEMBER 1, 2024. -*- Johnathan is the "gentleman who isn't afraid to fight" type, so let's come up with a team for him first. I think he would have a Lucario, at least. Not only is it a dog (lol), it's weak to fire and also senses others' auras. Lucario is the embodiment of vibe check lol

I'm gonna give them at least three, but the max they can have is six

Buh hmmm.... Idk what else he would have. (Btw feel free to chain on this comment and add your own ideas)

Seeing as they are in Victorian-era England, I thought it'd be a good idea to include mostly only pokemon you can find in Galar.

Oh, Johnathan would LOVE Boltund, let's add that to his team

Also Arcanine, I think his ace would be Arcanine

He would also have a Gallade, which I equate with being a knight.

So far it's Lucario, Arcanine, Boltund, and Gallade. For Johnathans team I mean

I can't really think of anything else to give him, maybe SirFetch'd?

Unlike Johnathan, Dio would not have the abundant resources to catch pokemon. However, he would probably have two or three really strong pokemon. I can see him having a really powerful Perrserker, since that's all he'd really get. I can also see him having a Zweilous and a Bisharp when he is first introduced. He has such high level pokemon at such a young age because he kinda had to, to survive. Battling earned money and put food on the table, after all. Later on, when he becomes a vampire, his Bisharp would probably evolve to a Kingambit. And seeing as he has Joestar money to buy Pokéballs, he could probably get a Golisopod. I can see him with a Golisopod. Later on, he w

So actually take the Perrserker off. He would only have four pokemon. His Zweilous would evolve later on in the series into a Heydreigon. So Dios team for Pt 1 would be Zweilous and a Bisharp, and later on he'd get a Golisopod and the rest of his team would evolve into Hydreigon and Kingambit.

Next is Speedwagon, like Katwolf said he should have a zigzagoon, and i think he ahould also have a dodrio

Oooo that sounds interesting, I also like the idea of Speedwagon having Dodrio