Alright, finalized team, but with a fun twist, backstory for each one:
Karlof the Mega Metagross: Gifted from Steven Stone, I've raised it in Mister Stone's honor, but Karlof envys his Metagross, idolizing it as his role model. When danger strikes he does exactly what Mister Stone's Metagross would do.
Bucky the Rotom/Heat: Met in Unova, he is crafty and intellectual, but takes these traits with great pride, often acting above the rest of the team.
Ash Greninja: Some guy who failed six leagues sent it to the wrong address and I'm not giving it back. It's constantly craving a battle, but is patient as well.
Mightior the Minior: Met in a cave in Alola, he's shy and disliked losing his shell, but overcomes this distaste in the heat of battle.
Tusks the shiny Mamoswine: Met in a cave in Unova, it takes pride in it's golden fur, treating herself like a frail treasure, dislikes working but is happy to help when no one else is doing anything.
Shepard the Alolan Golem: Met in a cave in Alola, he enjoys bossing the team around and giving orders, but when the time is right, he takes action
EDIT: Alright, I did have one question for my team. Should I replace Mamoswine with Alolan Ninetales?