Currently there isn’t an easy way to do this. Animations currently store the angle (doesn’t need to scale since it’s an angle) and the position (doesn’t scale, causing things to look wonky). I’d reccomend that if you make animations that rely on the position to be accurate, that you limit the character sizes accordingly.
Of course the animation isn’t going to scale; it only cares about the relevant Motor6Ds used to create the animation (and therefore their CFrame Transform property), not the size of your parts. You’re going to have to create the animation in such a way that it accommodates for different character scaling or configure your game to achieve the same effect whether that’s by enforcing a single size or making your own avatar sizing editor in-game.
You have the option of creating your own animation-ish system by overwriting the Transform properties of Motor6Ds so that you can adequately achieve the desired effect, though the trouble may outweigh the merit or usefulness to you of such a system.