I know you said we can pick anyone, but I think we should at least take into account each character's personality and the team dynamics involved. Someone might want to pick Ella and Bernhard due to their immense power, but Ella in practice might actually make fights harder because she can't resist testing/fucking with the MC and we have no idea what fighting alongside Bernhard would actually be like.
Personally, I'm going with Jake, Demi, Alice, Michael, and Alexis for a blend of power and versatility. Jake and Demi can potentially stop some fights in their tracks with their mental abilities. Alice and Michael are strong fighters with exceptional personal qualities (perseverance, bravery, loyalty, etc). Alexis has really powerful ranged combat abilities, and I trust her more than Danica. The way I see it this team would offer nonstop punishment for any potential opponent. Jake and Demi would attack their minds, Alice and Michael would batter them up close, and Alexis would slice and dice them from a distance. And the MC would presumably also be doing stuff. It all adds up!