Here are my ideas:

The Hyperthrust Capacitor would be rerouted through the shield emitters, thus instead of a separate capacitor (in all of the other modes), it would actually damage your ship
The airbrakes have a chance to fail if structural integrity is low
If there are any pits on the track, they will be disabled
Bumping into walls brings you to an instant stop (like in the original WipE'out)
The HUD will start failing if your ship is critically damaged
No side-shifting; You'll have to resort to opposite braking
Acceleration is automatic. However, you can still get a boost start if you're skilled enough (won't do you much good though)
AI is locked on the hardest difficulty
The race is locked on Zen class

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Now it is truly hardcore.