WALL-E seems like an easy one to slot in where Stitch was, and Elio feels like it could be an appropriate Monsters Inc. replacement, assuming it does well. I still think they should follow through on the electric lightcycle upgrade to the Speedway and bring a lot of the Shanghai elements that complement TRON to the main section of Tomorrowland. The Shanghai stage, for instance, looks about a billion times better than the one we have currently.
Most of the other attractions, restaurants, shops, and areas just need an appropriate amount of TLC. Like, why not replace the PeopleMover vignettes with Space 220-esque windows that give you "views" of vast Tomorrowland cityscapes and add some minor projection mapping in a few places? And as you said, the entrance needs to be something really visually arresting.