Agreed, you can't be expected to jibble the setup for just one person, and thereby compromise how it works for the 1499 others.
But as I said, if you make the ECE long enough, you get enough extra time that it shouldn't impinge on the normal arrangements at all - and Greenbank's produced an illustration of how it might work.
Failing that, if the team was happy to accept a 3rd party doing the registration and bag drop stuff for another rider (pre-arranged, with letter of authority etc etc), given that I live in London I'd be happy enough to be the 3rd party for anyone who wants to ECE it. (Obviously, not if there's a hundred and three potential ECEs ...)