How do keep character shape consistency while animation applied


the reference images are posted.

I have two characters sharing exact same bone structure hierarchy. but different proportions. I want to make from one character BP has two characters and the character can be switched by user UI. when it is posing default A pose, has no problem at all. But when It takes an animation it goes to “A” proportions which is the original one. the animation doesn’t have ‘scale’ and ‘location’ data but only ‘rotation’. How do I apply only ‘rotation’ value for each characters in order to keep the character’s original proportion.