Be careful what you wish for: coalition governments are notoriously unstable and ineffective... look no farther than Greece.
I would argue, and have in previous posts, that the two party system has worked exceptionally well for the USA. And it can continue to do so...
The central dysfunction, and the key to getting our society back on track, is the weakness of the center as one extreme has grown in power. I do not find the Democratic part particularly extreme, but I think important factions comprising a significant portion of the Republican party have.
Now those factions (fundamentalists vs corporatists) are in conflict over who should represent them -- and the party as a whole is weakened as a result.
Good. Let them take notice of what most main-stream Americans want, regardless of party affiliation: A good job, good schools, a future for thier kids, rich people that pay their fair share for living the dream, separation of Church and State, the government out of their personal lifestyle choices, NOT laissez faire, pseudo-libertarian, pay your own way and #$%$ the rest, home-educated, trickle-down, narrow minded, Fox-watching sanctimony.