New controller inputs are possible, a lot of them. The switch could be done with A+B, A+Y, A+X, or basically any two other bottoms beside A+(L or R). Also there’s two jump buttons, one could do something else, not to mention using a direction on the d-pad. The controller is far from being maxed out in terms of it’s use in smash bros.
With one of these new inputs, you can ADD a move to a character without changing anything else.
Back to the D-pad, if it’s worth giving up taunts (maybe not for new samus), using the D-pad could give the switching attack direction, or one of the previous button-combinations plus a direction on the control-stick or c-stick. So many possibilities