Back when I played Star Made some guys had a similar idea after a few test runs this is how they did it
1) Checkpoint system, racers had to get to each checkpoint get out of their ship get an item then run back to their ship
2) Limit to thrusters, ships could only have a certain amount of thrust blocks
3) Hazards, the first was automated turrets second was an artificial asteroid field.
1 made it so you didn't have to worry about having a specific track for racers to stay on, as they had to go straight from one checkpoint to the other.
2 and 3 combined made it so racers had to balance acceleration maneuverability and durability. Make a ship focused on speed and you'll lack that ability to quickly change direction and you'll be as tough and a wet paper bag. Focus on durability and the other racers will fly right past you.