An idea I would quite like to see implemented in the future along with a team online function would be to have a split screen team online feature.

This would mean that two players playing in split screen would be able to play as a two player team online. You would be able to easily discuss tactics with your teammate as they would be sitting close to you.

Races could be conducted with up to four (or more if hardware and servers allowed) and in tournaments the points earned by each player during the race would be added to that of the teammate.

The players could also be made immune to weapon attacks from teamates, or a penalty system could be introduced for such attacks.