I can think of two ways that this can be accomplished...

1) Create an Action Target Group with all of your characters in it, set the ATG to be the Target of whichever Mapped Keys you'd like, and then use ATG Actions to rotate characters in and out of said ATG.

2) If you're using virtualization (or maybe even if you're not) you can use Mapped Key Virtualization Actions to adjust what your characters do.