They did try out extra officials, one at each end, in the Europa League, although chances are thats more down to UEFA, rather than FIFA. Platini seems a tad more willing to sort out this debate than Sepptic Bladder.
Did have an effect on one game I know of, at Goodison, ref gave a goal kick to AEK but the byline ref overruled him and gave a corner. 30 seconds later, 1-0.
Will that be considered for Rio 2014 one wonders