I've computed the April 2008 through March 2012 rankings with AFC Challenge Cup matches as continental qualifiers.
Looking at the peak for each team in the rankings between April 2008 and March 2012, these are the 20 teams that would have gained the most. 18 of them were involved in the ACC.
Team - Peak in the normal rankings - Peak in the modified rankings - Difference
This will also help fans of AFC Challenge Cup teams see what to expect in the future.