I think I've seen scenarios and heightmaps with this theme. I like the idea myself, it would be interesting to see what kind of systems people would make.
However, there is (at least) 1 problem with this idea:
Ships and aircraft are usually limited on servers (and for good reason) so making a map with large amounts of water, which can only be crossed by ships and aircraft wouldn't make much sense. This would lead to people terraforming land between the two continents, and at that point, what difference would there be between a normal server and this "two continents" one?
A solution could be to not restrict ships and/or aircraft, but seeing as they are really easy to set up, wouldn't that take away some of the fun?
An alternative could be that you have to have a certain amount of profit from each individual vehicle category in order to win, this would be very interesting. However, seeing as I know Jack s**t about coding, I don't know if such a script is available, or even possible.