A pusher trailer with 2 wheels in no way shape or form is considered an automobile. In fact, the law makes ZERO references to pusher trailers at all. It's a gray area in the law that I happen to proudly take advantage of. When it's a trailer, it's not part of the vehicle, instead, it's simply being pulled by it.
If you have a regular motorized bicycle, and you pull a 2-wheel trailer, it does NOT suddenly transform your bicycle into an automobile. Where the engine is located is irrelevant. There's plenty of folks here with MB's that pull trailers like in the picture, and it does not make the bicycle an automobile, AKA car.
In fact, the law does not even mention anything about an engine powered trailer AT ALL. Regardless of engine HP or cc's. Sure, I can have up to 50cc on the bike, but there's NO limits to the cc's on a trailer, simply because the law or Florida Statues make no mention of it. I'm simply hauling my engine. There's no laws that say I can not possess or carry an engine.
The law is not open to interpretation or manipulation. You either abide by the law or you don't. If it's NOT listed, it's NOT against the law. It's unlawful to put something in a category of the law where it does not belong.