Nordic skiing (the other xc) does interval starts all the time (like, it's a standard race format, and until about 20 years ago was the only race format for most high-end races). Registration closes a few days in advance, field is seeded, lowest time wins.
Obviously you would end up with a not-small number of people in the same general area for the start, finish, and other logistics, but it reduces the number of athletes actually on course at one time.