Normally you just map directions from one location to another. But say there are alternate routes and you want to specify "the back way" or something. You would enter a Waypoint choosing the "Waypoint Tool" and clicking on the map to stick a "pin" at a particular spot. Alternately, you could enter a Waypoint Address into a text field. Then the directions would be recalculated to pass through that point you specified. Even better, perhaps a user could click on the highlighted route and drag it interactively. The route would snap to roads that are a viable route between your chosen start and end point, and pass through whatever Waypoint Pins you've placed. Or users could enter start and end points and begin "drawing" a path that "autocompletes", snapping to roads as you go. Think Photoshop's magnetic lasso tool.
That way you could help guide the path visually by using this interface to weight the solver. Then you would have easy, clear directions for each step of the trip that you have specified. "Wouldn't it just be easier to ignore the first part of the Google directions and start following them once you are already on the interstate?" Sure, but what if you were trying to give directions to someone else who isn't familiar with the local area? "Custom directions" would be very useful for businesses who could link to them directly from their websites. Visitors could enter own starting address to get full directions to your location, including all the back roads and shortcuts that you know are the most efficient way to get there.
Perhaps you could even enter notes at certain steps along the way, like "Look for the big Fireworks sign on the left". All of this custom data could be likely be included in the URL string so setting up accounts would be unnecessary. The direct link for your custom directions would function through GoogleMaps and maintain the interactivity of the full system instead of having to be static. This Waypoints feature could also be tied into a system for trips with multiple destinations that will figure out the best route that passes through them all.
Of course, in able to draw or drag routes around on the map interactively, you would need to be able to switch from the standard "click-and-drag-to-move" default mode to this "Guide Route" mode. Perhaps the right mouse button navigates the map when "Guide Route" mode is active. Like Adobe's "Hand tool", except the spacebar is already used for pagedown in most browsers and you wouldn't want to override that. In fact, since there are not any context menus defined, the right-button navigation functionality could be on all the time and still maintain a right-click context menu for "Add Waypoint Here" or something.
Anyone have any ideas of how practical it would be to have that kind of added functionality? I'd love some input on the idea.
x-posted to personal journal