Historically, vehicles actually did have completely interchangable motive components. They were called horses.
It would have been difficult given the state of other technology at the time for the inventors of the internal combustion engine to have supplied it as a drop-in horse replacement for your carriage, but you could kind of imagine that working with current technology.
I don't like the impulse to regulate, especially as a formative measure. Regulating new technology before industry has time to experiment seems like a recipe for high prices, few choices, and low competition.
It would have been difficult given the state of other technology at the time for the inventors of the internal combustion engine to have supplied it as a drop-in horse replacement for your carriage, but you could kind of imagine that working with current technology.