Really just one thing - a green at the turn station after the previous station displaying a yellow. It would eliminate the guesswork of "no passing until after the last component of the incident causing the yellow flag."
Isn't "The yellow flag is in effect until a green flag is shown at a subsequent turn station" much easier to interpret?
I'm sure this has been discussed before, but it shouldn't be a big deal because green is in every turn station's flag set, always discarded to the side.