The four extra campaigns are definetly neat, but limiting the player to only play them with the cars for the base game and making the added ones the reward for beating these extra storylines definetly works, but feels less exciting than to go in trying to figure out the new drifting mechanics of the new vehicles.
I just disagree with the design philosophy of structuring the DLC in this way, as I found myself having unlocked all of the cars, but not really having anything to do with them. By the time I had them all I just felt like needing a break from the game.
The mechanically incredibly tight game that is Inertial Drift still works throughout the experience. It's my favourite arcade racer and getting back into it brought me a lot of joy. The new tracks felt a little confusing and counterintuitive though and the overall feeling of this experience is pretty similar to the base game.
The bottom line of this is, that the Twilight Rivals Edition works wonderfully as an extension of the base game, but does not break any new grounds. The new little opening sequence is nice though and the price is really fair.