GalacticPetey
Donkey Kong
It takes years to properly create and balance Smash characters. The amount of work and detail Sakurai and his crew put in is crzay By making Smash a bonus "brawler mode" you run the risk of having a shallow imitation of Smash. You'd have to cut corners or just straight up port Smash 4, at which point you should just expand that game instead of tossing in a watered down version as part of a Mario Kart clone. The two games have such fundamentally different development cycles that such an idea is foolish.