I actually recently had an idea that would reward perfect laps with improved speed; technically though, it would be more similar to Perfect Zones:

For every ten seconds that you are in constant motion (and not going in the wrong direction) without taking damage from a wall or falling off the track will increase your top speed slightly. Getting hit by weapons doesn't count, because there isn't anything you can really do about that... Though your top speed would reset if at any point you hit the wall or complete an imperfect lap.