I don't think it was intended this way, but the two party system works because of the way our gov't and elections are structured i.e. electoral college, districts drawn by states every ten years, etc.

The only way to make it possible for more than two major parties to thrive is to totally change the federal gov't to a parliamentary system like they use in Europe.

That would also force new parties to be more comprehensive in their platforms. The purpose of "third" parties today is to play spoiler with one or two issues that a majority agree on, in the hope that they can steal enough voters to force one of the major parties to adopt their issues to get the votes back. That's how the Republican Party started.