As a Roblox developer and animator, it is currently too hard to anchor certain body parts to a position in a quick and easy manner whilst keeping it consistent and non-shaky[1]. Inverse kinematics helps this a lot as it only requires me to move the “EndEffector” part for the entire structure to move, but in some cases this feature could actually make it harder to align joints across the three axes.
For the non-animators out there, onion skinning is similar to using a lightbox when doing traditional animation or final-drafting for art. It underlays a translucent previous image (in this case, keyframe) below the current image (keyframe). This is good as it allows animators who animate frame-by-frame to make modifications to existing keyframes without constantly switching back and forth - in traditional art, this is the same as looking at one paper far away and then trying to replicate the same change on your current paper. It is also good for animators because it allows the non-frame-by-frame animators to anchor certain limbs or extremities to a place by overlaying said limb/extremity over the onion skin.
If Roblox is able to address this issue, it would improve my development experience because it would reduce the amount of time it would take to make changes to a keyframe relative to another one, perfect for gauging what spacing I should take relative to another keyframe, where a limb should be placed to match another keyframe, and so on.
It would also be highly beneficial to allow onion skinning past multiple frames. This would be fantastic for animation concept art like tutorials! Bonus points if the onion skin is a different color for every frame.
I believe the solution should be “simple” as well, every selected keyframe would clone the current rig and apply all Motor6D transformations to all joints. Make the parts in the cloned rig a different color, apply a LocalTransparencyModifier, and voila. There’s your onion skin! It would also be preferable (if possible) to have a color indicator above (or around) the keyframe diamond to indicate what onion skin corresponds to what.
I use Moon Animator quite frequently, and the Roblox animation editor is so very appealing, but there are some pretty vital features like this one (and quite a few others that I will make a feature request for) that are missing - and this makes me sad, because I believe that the UI and UX that the Roblox Animator has is so wonderful, but this animator focuses on the qualities of life versus the actual necessities.
Generally, I believe that proprietary plugins should not be overshadowed by third-party plugins, rather, they shouldn’t be made completely irrelevant in favor of a third-party solution; in that case it would simply just be better to deprecate the Animation Editor in favor for Moon Animator.
[1] this could just be because i’m a bad animator (please don’t say this my ego will die)