I kind of liked the idea, but couldn't figure out how the story could be staged....I guess that's a reason to see it!
SPOILER ALERT: (NOT A BIG SPOILER, it's set up early enough in the show)
Since it's a musical, it was set up early that the characters will step away from the vehicle when they're in their minds, like for the songs.
Also, IIRC, in the movie, too - each person got a very very short periodic break to take their hand off the car.