I've had an initial stab at doing one and whilst delving into the details of the XML files, they seem to be incredibly spartan, particularly in the Race portion, with no number of laps completed or total race time.
There are also some odd entries, e.g.
<MultiplayerRacePlayer>
<BestLapTime>92762</BestLapTime>
<Car>Zakspeed Capri</Car>
<Position>3</Position>
<Username i:nil="true"/>
</MultiplayerRacePlayer>
with no username. Was that an AI car perhaps?
Is the JSON output the same data just in a different form?