Not sure how much the propeller system costs, but it does have some advantages when put to use. It increases efficiency and economy in most cases for the user. It also helps provide the user with more maneuver control, so it adds to the ability to control as well as gives additional power.
The CPP system provides the driver with the ability to jump in the vehicle and cruise away in the water. This definitely would be useful in the case of a tsunami or major flooding. My concern would be in the event of debris in the water, how will the propellers handle this if they are hit by building materials, tree logs, and the like??
Good idea, but has challenges to overcome! I guess one could maybe place a protection cage over the propellers to help provide additional protection.