Tournements: I think, that when they have multiplayer, they should have tournements, like it starts with 16 people, thens theres 8 people, then 4, then 2, then there is a winner, and there would be loser brackets to determent specific places.
Big Races: I think that another category, could be big races with a bunch of people. like, with 50 people, all racing together, wouldn't that be cool?
Ranking system: well, when they would have this, i think they should have a ranking system. like each time you play, depending on your placing in a race, you get points, if you do good, you gain points, soon raising your rank after accumulated points, or if you do bad, then you lose points, possibly lowering your rank.
I know all this is alot of work, but games take time to think through, develop, test, fix problems, then test again.