Level-5 has done some experimenting in the past by making the characters cross over in each others universes from time to time.after all these years ive finally got to play ni no kuni and honestly it makes me want a big level-5 corss over with layton, nate and oliver teaming up
Layton & Co have shown up as a team in Inazuma Eleven or Yokai's in Yokai Watch.
I suppose a generic Level-5 kart racing game may not stand out much as its more or less done to death by other companies but perhaps they could expand on what they did with Inazuma Eleven and have a few Level-5 franchises appear as special teams there? (That you can hopefully acquire this time)
Or special guests in a Fantasy Life game.