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If a banding card targets multiple characters to be banded into battle, the characters are banded in simultaneously. The banding player chooses the order in which the special abilities activate, provided the rule for any “choose opponent” special abilities are activated last (see Choose Blocker or Rescuer). The special ability of each character is completed sequentially in the activation order.
I agree with the principle behind what you're saying, except that the REG specifically says all characters enter battle simultaneously. Nobody enteres first, second, etc. Once all characters are banded in the person who played the banding card would get to choose the order that the SA's activate on both the Heroes and Evil Characters.