Maybe they could add new playable characters in Solo Mode, like Dark Pit, Palutena, Viridi, Magnus, Medusa, Phospora, Pandora. Maybe they could even give each character their own solo story. If they go for that route, Hades and Thanatos could be nice.

Maybe they could add in alternate costumes or palette swaps. Pit and Medusa could have classic outfits. Pit could don a replica of the Three Sacred Treasures. Pit, Palutena and Dark Pit could have their Super Smash Bros. Palette swaps.

If anyone has any ideas for a sequel, like stories, mechanics, features or weapons, feel free to share them.

I haven't played that much Uprising, but thats a cool idea!