I love the idea of being able to transfer most anything that's purchased for an event in the future.
Concert tickets, sports event, bike race, etc.
It helps ensure participation numbers and recognizes that life happens and sometimes people's plans must change.
A transfer fee is quite reasonable since new rider information must be entered. And a waiting list is quite reasonable for an event like DK where there are more applications that spots available. It's all randomly chosen(supposedly and for the most part) as is, so continuing the lottery selection into a waiting list would be simple. Ensure the transfer fee more than covers admin work, and what's the harm?