Give Runners Choice During Race Between Half-Marathon and Marathon

My running training is rarely a matter of me establishing a set amount of miles beforehand and then running them.  Instead, I will run as circumstances dictate, both those external and internal.  For example, I may be operating one day under time constraints that limit the amount of running time I can spend.  Or I might be feeling under the weather or have a slight injury to nurse.  But when I have the flexibility of time and I'm physically feeling good enough, then my mileage on any particular run becomes open-ended...and it's always seemed to be that way, ever since I resumed the activity in 2007 after essentially ignoring it for thirty years (exception: a short three months running period in early 1998).  Sometimes this way I will go on and on with a run, racking up huge mileages...and sometimes I'll stop at a lower level.  Which brings me to a proposal about some of the long-distance races I've entered before...

As I see it, there are two types of half-marathon races out there: the races that only feature that one length of the course and those which combine the 13.1-mile half-marathon course with a 26.2-mile full marathon course.  One of the latter is coming up on February 15: Gainesville's FivePoints Marathon/Half Marathon, the two races being run concurrently.  That's important with regard to my proposal...

In the FivePoints races, both events run the same course for the first 13 miles.  Then, just as the half-marathon event is almost finished, all of the runners encounter an intersection with directing signs.  The arrow pointing to the right is for the half-marathoners to follow and finish up their almost-completed race, while the left-pointing arrow directs the marathon entrants to continue their race another 13-plus miles.  Of course, the way things stand now, there's no choice involved here: the runners have either signed up for the half-marathon or the marathon and they can only finish in that event for which they are already registered.  But suppose, just suppose...

Suppose that there is a third option for runners that gives them the opportunity to choose to go either left or right at that intersection!  That would be awfully intriguing for someone like me who usually keeps on running in my training when I'm feeling strong.  It would be a tantalizing decision to make, indeed.  It reminds me a little of the Matrix movie scene when Morpheus presents Neo with the choice of choosing the blue pill (end the adventure now and go back to life as you want to believe it) or the red pill (and see how far down the "rabbit hole" goes)...