Just another suggestion. Why not add speed courses for testing over-land and over-water speed. in the real world, racers at places like the Bonneville Salt Flats run over a 1-3 mile course. They run the course in one direction, turn around and run the course in the opposite direction, The times for the 2 runs are averaged together and determines what your speed was.

In simple planes could be done as a new game mode or a discover-able location. The rules would be simple, "you must stay on the course." Meaning that your vehicle must be controllable. As for water speed, your craft cannot break contact with the water for more than a second. Otherwise it will be considered "airborne" and disqualified.

A flatten-out section of Maywar Island would work for over-land speed testing. While over-water could be done just about any where else.