Why not go top-down? That could make it unique in the kart racing space. Or perhaps choose a different perspective! Have you ever played R.C. Pro AM on the NES? It was definitely the best racing game on the system, and it used kind of an odd isometric view, but it worked really well!
EDIT: As in RC Pro AM, having a top-down racing game has somewhat of a side-effect: Since you really can't see what is coming in front of you, a lot more emphasis is placed on learning the tracks and knowing how and when to react, and also creates twitchier gameplay, as compared to behind-the-car views where the gameplay is more related to seeing the coming terrain and knowing how to react to it. Neither is really better than the other, but they are definitely different
