Unconventionally, your Meister/Weapon team includes more than two people. For each time this upgrade is bought, your team includes an additional Weapon or Meister.
Each member of the team starts out with the same level of compatibility with the rest as A Dance of Souls normally gives; this allows fantastic teamwork between all of you, allowing multiple Meisters to fight harmoniously using the same Weapon, either passing it to one another as they are fighting or even using each other's weight and momentum in their fighting style. Similarly, multiple Weapons can take turns wielding each other, using quick shapeshifting to dodge attacks.