We're not fully using those accounts and they're not working as well as they could. Let's take those accounts we already have and make them work better, rather than creating a new system of accounts.
To improve the style of the 401(k), we should recognize the power of inertia in human behavior and enlist it to promote rather than hinder savings.
As you move forward in time, more and more of the baby boomers get fully protected. Past 2009, the bulk of the baby-boom (generation) is falling under that protection, and it becomes almost impossible to sustain that assurance.