GfS, I recognize some of your banter as tongue-in-cheek (plus I agree with some of what you've been saying).

My skinny dipping scenario, though, was not really so far-fetched.   We have two main "clothing optional" beaches near Portland (as do some other cities such as San Diego), and there was a time I used to frequent them.   It wasn't a good idea to take your valuables with you to the beach itself (not even money, because there were no booths selling anything), and unless you were the driver (we usually carpooled) you may not have left things like your credit cards and ID in the car. Vehicles parked in the lot or on the side of the country road were routinely broken into.

Now, some men's bathing trunks have places to safely stash an ID card, but even if you're not completely au naturel, most women's bathing suits don't.    The kind of law some are proposing would leave you vulnerable to harassment, major disruption of your day, and possible arrest and incarceration just for not having documentation of your legal residency with you at a time like that. I used the "skinny dipping" scenario because that one doesn't even offer the remedy of sewing a special little pocket into your Speedo to hold your "papers."

BTW, I keep hearing on radio that Arizona law ALREADY permits law enforcement to ask for proof of legal immigrant status or US citizenship if you are stopped for some other criminal code (and maybe even traffic law) infraction.    The new law changes it to
1) law enforcement MUST (not "may") ask for such proof and can be sued by anyone if they don't
and
2) this applies whenever there is "lawful contact" between law enforcement and an individual - not just when there is probable cause to suspect that a crime has been or is about to be committed.

If the law is currently being "tweaked," we'll judge the final product when it goes into force.   But as it stands, I think there is great cause for concern about undue racial and ethnic profiling and about violation of the 4th Amendment.