Posted: 24/11/2016 at 12:46
It would work if you declared that any runner who hadn't collected their number (say) 20 minutes before the due start time forfeits their entry. Potential runners arrive before that, fill in the entry, then join a queue with their cash ready. 20 minutes to go, they start getting the unused numbers, details can be entered into whatever system the organiser is using in the same way that entries on the day would be.
Or, make it easier for runners who aren't going to show up to let the organisers know, even on the morning of the race. Right now, if I decide that I'm not going to run, there's no point letting the organiser know because my number is just going to sit in an envelope in a box anyway. If I had a text number to use to let them know they could re-sell my number then I'd use it, even if I wasn't getting my entry fee back. I'm a runner, I'd want an unused entry to be used somehow.