The 2018 marathon was my first runDisney event. My on opinion, which really isn't worth anything, is there should be two groups up front. First group should be elites. Second group should be "qualifiers" (as in Boston) or people who can prove they have the potential to finish in say 4:00 or less, that aren't in the elite group.
Both the elite and the qualifier groups, should have different bib colors than the rest of the runners, and there bib colors should different from each other. As for the rest of the field, corral placement should be based strictly on when you signed up. Aide from qualifiers there should be no POT submissions permitted. You sign up early, then you end up in Corral C. You sign up late, you end up in H. This way, people who are close to Boston qualification can't complain they got stuck behind people running a 6 hour pace, and lost their chance at qualifying. And in traditional fashion, Disney could set up an upcharge for people who want to pay their way to Corral C. Otherwise, everyone else is in the same pot. If using different color bibs to differentiate the elite and potential qualifiers from everyone else doesn't work, then I doubt any set up could be policed. One other thing race organizers could do is change the bib color for all corrals and not release the appearance of the bib until you go to pick up your packet. That way, someone can't photoshop or create their own bib at home with a different number on it and use that to move up into an earlier corral. Even this setup wouldn't stop people from hopping from corral t corral but different bib colors should help. Anyhow, that's my two cents.