IK Retargeter can work as a kind of retargeter setup, where you can choose what animations to retarget, but then you need to create another AnimBP for that character and use the retargeted animations, or you can use IK Retargeter to work in realtime, where you create a dedicated AnimBP for each characters, but inside the AnimBP you use the “Retarget Pose from Mesh” node, which uses the same animations of your “base” AnimBP, and then applies a retargeter setup on top of the animations.
I’m not sure about performances, but I guess that you can have your main character and a child which you can swap in realtime, based on inputs, like analog directions on the gamepad.
By doing so, you have as many AnimBP as the characters you want to use, but you can act smart and “load” one the one you need at that time based on inputs.