Does Nate have the notetag with something like "<battler name: Nate Backsprite>" in his notebox? As for the battle sprites it's set up with two sprites. One is a single frame of the animation, while the second is a strip with a width that is a multiple of the first sprite, which then is used to determine the width. You can add a battle pose for Pokémon, but it'll require a bit of scripting to do as you'd have to restore the original Yami Holder's battle script and then readjust the elements of the script.
As for the questions on game mechanics, I do like to create new systems, so let me know your idea.
As for the questions on game mechanics, I do like to create new systems, so let me know your idea.