Hidden/Bonus Cars in the Bonus Minigame

Would there be anyway to mod the game so it allows bonus cars such as the Black - Ferrini be able to be used?

I always see cpu's using them

it is possible, but it might be very hard to do.

Adding new vehicles to the rewards.mfk will simply crash the game upon launching the Minigame, so I believe the bonus game is somehow hardcoded, which means that adding those unusable vehicles won't be that easy