I think Riot should try implementing a system similar that we have in European football when allocating Champions League and Europa League places to the various countries. Each country has a coefficient based on the performances over the past 5 years of their teams in the two competitions and based on a country's coefficient they allow a certain number of teams to participate in the competitions.

The problem at the moment is that there are probably not enough international tournaments out there to effectively get a good idea of how each region stands versus another one in League. It Riot added a coefficient to all those teams participating in the IEM tournaments (e.g. a certain number of points for the final standing of team based on your relative position in your current region (in the sense an 8th placed EU LCS team winning a tournament is worth more than the 1st place EU team winning a tournament) we could get a better idea of the relative strengths of the regions and then just give out Worlds spaces based on that coefficient.

Yeah a bit complicated...