Practical example - friends are planning a long route out. Reality is we'd like to place one or more "decision points" on the route where we can decide to take one of two paths. This might be because of running behind schedule, or unsure of personal preferences, or we won't know of a certain state of affairs until the day (whether a colleague is joining us or not, for example, or whether an event is taking place).
At the moment, you'd create multiple copies of the route and if the situation changes, load one of the alternatives (or just let the navigation find you an alternative path to your destination if, for example, you're running out of time).
It would be cool if we could pre-set "decision points" in a route, where an option for an alternative to the original defined route could be prompted to the user. No input, then the route continues. But the user may choose an alternative route if they wish (a simple "Do you want to choose alternative route XYZ?" prompt, times out after 30 seconds), in which case it's loaded and followed from that point.
I am guessing defining multiple tracks in a single route is going to be problematic from a software architecture perspective, but even if it's just allowing a switch to another route based on location on the current one, that would suffice.
You could even do some funky, cool things like "if behind schedule by more than X minutes, prompt user for alternative route 2" but... well... we might be getting ahead of ourselves