Sailor here,
Altitude is not a real (measurable) issue on the water. I'd suggest the idea to add content that portrays the angle to the next waypoint (either a visual or a measurement in degrees). This could open the way for efficient tacking (going upwind). BTW, I could imagine this would be too major an alteration. On the other hand, such a feature could come in handy for land driving as well btw. (i.e. for visualizing the general direction).

Anyway, absolute distance to next waypoint, too, could be informative as well and/or alternatively (i.e. to mark the 90 degr. position to a buoy, although 90 degrees normally is 'late' for a tack).

Cheers, modRana already is very cool. As said, maybe what I said is reasonably undoable, but I just wanted to describe from sailor's point of view.