Mario Kart 9: 10 Gameplay Features Fans Demand
2. Track Creator/Editor
Who doesn't want this??
It's a bit of a no brainer given how far level editors have come in recent years, whether in triple A productions or even on Indie games. Nintendo even has its own successful level editors available in Smash Bros. and Mario Maker.
Something akin to a track editor was included in Home Circuit and saw people constructing their own courses in the real world, but that requires a large amount of space in which to work and not everyone has access to that.
We've see the breadth of what communities can achieve, not just in terms of design, but also innovation, with many folks breaking and expanding the genre's boundaries. New rules and new ways to play are being created all time at an alarming rate; if you give someone the tools, then they'll build it.
Other series, like ModNation Racers and LittleBigPlanet Karting have achieved a functioning track editor with mixed results. Dreams on PS4 allows for just about anything, including racing games, but the tools aren't perfect; so think what Nintendo could do.