This is an argument for America switching to the parliamentary form of the legislative branch.
Primarily, the parliamentary form of government reduces the lack of action found due to partisanship in our current system.
With a parliament, we would have a more diverse representation in our legislative branch. This might increase discord, it would also increase cooperation on legislation. Take, for example, the legalization of marijuana. I believe the Democrats and Libertarians would be able to overcome opposition of the Republicans which is mainly economically based. The Republicans have little regard for the welfare of the poor, concerned more for the lucrative bureaucracy that has grown up around the drug war.
We would see coalitions around specific and constructive legislation able to enact useful laws. With the current system of effectively only two coalitions, there is little cooperation with partisanship trumping good sense most of the time. The result is national gridlock.
A parliamentary system would encourage the growth of fringe coalitions like the Libertarians though probably not to the point of domination of the process. I personally am a Democrat though I agree with Libertarians on a number of issues like the legalization of marijuana. It would be nice if my personal beliefs were more accurately reflected in the actions of the legislature.