If they aren't good, it would be at least fun if they were varied. Anyone remember the old N64 game Perfect Dark? The combat simulator mode enabled you to pick from a pretty wide range of bot personalities to fight against. A few notable ones:
Judge Sim: Will always hunt down the opponent winning
Kaze Sim: (Short for kamikaze) Will always go in for the kill even if their chances of success are low
Turtle Sim: Has extreme shielding
Speed Sim: Unusually fast
Peace Sim: Will go around disarming opponents
Meat Sim: Just really low skills (GT7 AI, basically)
Rocket Sim: Will always prefer explosive weapons
Fist Sim: Will always use fists only
It wouldn't work for the single player, probably, but for custom races having some personality in the AI could be really fun. Some ideas:
Late Brake Sim: Will always try to dive bomb other drivers (Gan San?
)
Shall Not Pass Sim: Will always try to move to block others from overtaking
Drift Sim: Will often oversteering through the corners (Dori Dori)
Loophole Sim: Will always enter races with overpowered cars
Sato Sim: Will drive consistently well over the limit of the car and frequently crash and/or wear out tires very fast
Slipstream Sim: Will relentlessly follow slipstreams in races
Gutter Sim: Will use runoff areas gratuitously for advantage
Pinball Sim: Will use track walls gratuitously for advantage
The real problem, still, is that none of the above would be fast enough to make their personality count for anything.