Plausible in the sense that you would accept having a "joint" account with the govt. People don't do that now so it seems unlikely they'd be very willing later. I think the idea was that thru a series of moves the govt convinces people that having a joint account with them for their own protection is a good idea. Personally I can't imagine many people feeling good about having a "joint" account with the govt now or in the future.

Be safe, Let Big Brother watch over your money.

Multi-sig is just what it's name implies - multiple signatories [addresses] needed to spend the money. A backup wallet is only an example usage based on the idea that the backup has both addresses present whereas the normal wallet does not.