Perhaps some system which took into account results from lots of different ladders and tournaments. Tennis seedings, for example, aren't calculated from the results of Wimbledon alone, but from lots of different events from around the world through out the year.
The difficult bit would be working out the scoring system. There are so many different settings and ways to win in SEIV, and also a victory against an unseeded/ low sedded player would have to count very differently to a win against one of the top ranking players... The more I think about it the less possible it sounds
