It would be super helpful if you add hotkeys to the program and brushes for shading and effects plus extra animation features for effects and easier Pixel Art Animation in which you can copy and paste/move layers of your character so that they more easy can be animated without having to redo it.
I think UnionSkins for Pixel Art Drawn animation would be a must to and a preview that shows the art work and auto plays the animation would be super cool too so that you can live see the changes you are making to your animation in the preview that automatically plays in a loop.
Last but not least the option to import 2d art from for example Photoshop, Illustrator or Affinity Designer and the option to then create a 2d rig with custom 2d mesh skinning options and keyframe animation possibilities really would make the software a super killer program.
It's pretty much all the features I have been looking for for a long while.