I like the idea of being able to play as all the opponents as preset racers in the car selection menu, in addition to the stock presets in the base game. But I think the opponents that are part of the car sets tied with the champion racers should need to be unlocked with said car sets. For example: Beating Captain Redbeard unlocks the pirate car set, which in turn unlocks Captain Redbeard, Governor Broadside and the other two pirate themed racers as presets, while beating King Kahuka unlocks the Islanders car set that unlocks both him and a fellow islander racer as presets. The same also applies to opponents based on the car sets themed after Batlords, Adventurers Desert, Adventurers Jungle, Alien and Rocket Racer in respective order of the other champions you face. The same can also be applied to Veronica Voltage if you beat all her best times in the time trials mode. It's just something I thought would be a nice addition for the sake of progression, even if it may be a no brainer.