The only Mario Kart games that used old tracks were the GBA, DS, and Wii iterations, but those were in addition to several new tracks. Those games had twice as many tracks as the rest of the Mario Kart games, so I don't see how that's a problem at all.
Double Dash!! added 2-player co-op in the same car.
Mario Kart DS added online, and missions.
Mario Kart Wii added motorcycles, tricks, wheelies, and tournaments.
When Perfect Dark re-used a few of our favorite stages from GoldenEye 007, did you consider Perfect Dark an expansion?












