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>Trainer Type
>when starting a new game, you can specialize in two types
>damaging moves get a 150% damage modifier if they're your type
>STAB moves get a 200% modifier
Why is this not a thing? Crunchwise, it deepens the meta and leads to new possibilities for rounding out a team.
Fluffwise, it adds more distinction to individual trainers, and and finally explains why NPC trainers usually only have one or two types that they specialize in.