Just recently I've been getting anoyed with some racers who just take no notice of blue flags. They carry on with the blue flag message pasted across their screen like they're on a sunday drive.
My suggestion is an optional time limit in the server config for the amount of time a blue flag is shown to someone before they are removed. If they don't yield within the set time limit they are moved to spectators or pits, to move them out of the way and/or race for disregarding the blue flags.