"Nationalizing" 401K's is a akin to Congress overruling 40 acres and a mule for each returning soldier from the Civil War.
Subsequently doing just that, ex soldiers burned down Washington DC. Congressmen ran to the Capital, as memory serves, and overruled, their withdrawal those benefits.
On the other hand, your little sentence, instantly revert accounts to pre deflation levels, would gift about 400K for every 600 remaining in older accounts, and that would occur just about the time $5 TRILLION hits inflationary streets. The current rate of payback on that kind of investment is 8%, it hit 13% under the worthless Carter years.
So whattya want? Go it alone on 600K and hope you're Warren Buffet, or let these jerks give you an IOU and pay you 8-13% on a million?