Every farm has some old, rusty wrecks in a barn or on a field!
So why not bring it into Hayday?
You could have it as decoration (Restoring the vehicles) or something to travel in to a different area that would take longer to get to. It could be something for the town, a new building that allows cars in the town, like a proper town has. (More realistic). A Garage could bring more visitors, or vehicles.
The idea obviously needs expanding from for it to get anywhere!
But its a idea that might, in the near-future, get somewhere.