For paper2d:
Flipbook have an integrated workflow like persona for 3d animations.
Revamped Tileset and Tilemap functionality for collision handling and performance improvement. Specifically being able to report which tile is being collided. (probably look at Game maker 2 since they pretty much did what Michael Noland was doing.)
Easier access to manipulate a tilemap programmaticaly per tile.
Easier ability to programmatically use a tileset on a tilemap.
Material functions to easily recolor specific colors on a texture without requiring any blurs or aliasing.
a hidden easter egg in the engine that can only be accessed by hitting ~ and then typing in disco and it spawns a disco ball mesh with spot lights and plays a funky song sound cue to finally make any multiplayer game on the ue4 actually have a proper disco command.