I like your idea, but it just brings to mind how fragile all of our digital media is, not to mention the surrounding tech necessary to read and understand it. What we know works is to press your message to the future, grocery bill, whatever, into clay and then accidentally burn the city down around it – good for millennia.
I think op is right. A new law that says you have to own real estate to vote would have been unconstitutional before and is not now.