I would like to see the ability to upload a series of streets via the API and have it become the in-game route. This would allow plotting routes based on things one would encounter on the way. (For example, a route that maximized the number of a certain resource one would pass.)
This would make a great feature addition to the Glitch Atlas site I'm now working on (glitch-atlas.info). The user could pick one or a couple resources and it would plot a route that maximized the number of those resources they would hit for a certain distance traveled.