5. Difficulty
I consider myself a fairly average gamer within the racing genre, yet when playing with my friends on 150cc or Reverse (supposedly the most difficult setting), one of us inevitably finishes in 1st place almost every race. The CPU should be challenging on the hardest difficulty settings, really testing human players to compete for places amongst them. Having said that, in other regards the game is too difficult advanced technical techniques such as snaking mean youre concentrating too much on exploiting the game and every race becomes somewhat mechanical and formulaic, with newer players completely unable to compete against the more practised ones. So firstly I would recommend making the gap between the different difficulty levels much bigger with 150CC being a genuine challenge. Secondly, Nintendo should take care to keep the focus on players reacting to a dynamic, changing racetrack (instead of exploiting the driving system) which will ensure varied races that maintain their appeal for everyone playing.
4. More Vehicle Types
Does anyone use Karts any more? The inclusion of bikes in the Wii U version, while not enough to propel the title to the dizzy heights of the first 2, certainly gave a much needed fresh lease of life to the franchise. Mario Kart 7 also included Hang Gliders, which didnt change the core experience much but also helped add a little variety. Why not extend that by including other vehicle types? Now, Nintendo certainly doesnt lack resources to inject into the Mario Kart series, and they should try to improve and vary the core game-play experience instead of just suffocating the gamer with additional content. Which brings us to...