Eight states allow for common law marriage Common Law Marriage by State Most US states do not support it or have stopped supporting it as of a certain date.
It's not a wrong thought, just a matter if it can be done to a level that helps enough. Whatever they do manage to implement will likely be one part creepy, one part neat for the rest of us.
It's not like it's $20 bills, those are $100 so people generally give them an eyeball at least. If they couldn't pass that they'd be a complete waste of time.