Let's be honest - if sparrow racing ever comes, it's a long way out. That's a whole new mechanic, and I think we'd all prefer them working on new content/story/nerfing blade dancers (jk hunters!)
THEREFORE:
Let us take it into our own hands. In my experience so far, venus offers the best "lap" so far. The moon is also plausible. Mars, I am not sure because I tend to get lost there. Earth forces tunnel sequences to, but you could set a target such as skywatch etc
So... form a fireteam, patrol venus (or whatever), hop on the sparrows and hit the gas pedal. First back to the spawn point wins. Have mics to maximize trash talk. Report epic race stories to forum instead of complaining about stuff.
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Wouldn't need a new mechanic. Just checkpoints.