Have you read Nudge? Given that it's the major popular source on the subject, it somehow seems incongruous to have a post with a major section on soft paternalism (they use 'libertarian paternalism') which doesn't even mention it (or at least the name 'Richard Thaler'). Save More Tomorrow is a real-life version of the pension plan you suggest (private, rather than government-run) which has had great success.

Libertarian Paternalism is almost exactly why I started to read the biases literature in the first place - it's the application of knowledge about the way people think/behave to economics.