As much as I'm looking forward to Mario Kart 8, I'm so disappointed at the lack of modes in the game. I mean, is it so hard to come up with some interesting/fun non-racing diversions besides balloon battle? That was one of the things I loved most about Sonic Racing Transformed - there were several different types of gameplay that were just as fun as racing. Traffic, boost, drift challenges, etc. Hell, the game even had bosses (they were not super well designed, but still fun).
I get that Mario Kart has been mostly about the racing (although for my friends and me, we played battle mode more than racing most of the time tbh), but I don't see why they don't experiment with different gameplay types. They did this somewhat in MK DS with the mission mode, but they haven't really brought that back in full swing since then.