Let's allow anyone to add any info.
Wasn't that the original spirit of Wikipedia?
Just suspend disbelief (and perhaps reality) for a few minutes and imagine: the world's greatest source of information, created through the sum of human knowledge.
Actually, that sounds like the Wikimedia vision.
Imagine a world in which every single human being can freely share in the sum of all knowledge. That's our commitment.
What if we assume good faith that every contributor shares this mission and is dedicated to pooling their knowledge into mankind's greatest compendium of information? If they did—and let's extend our assumption that their knowledge was factually accurate—Wikipedia would be comprehensive and efficient, verifiability aside. If we could take for granted that no edit introduced untruth and was made for the benefit of promulgating the sum of human knowledge, we would have reached the ultimate goal—and included more useful, relevant information than just what independent reliable sources could verify.
Even if we drop the assumption that all of the information contributed was factually accurate (while maintaining the assumption of good faith), other users would end up correcting inaccurate information, removing unnecessary details, restructuring articles for clarity, etc. The end result for most articles would be a sort of equilibrium state in which articles would eventually reach a stable state of good quality, i.e., requiring no more major or factual corrections.
But for some articles, edit conflicts and wars would break out. Perhaps an editor (or faction of editors), in good faith or not, disputes what another editor (or faction) changes in an article. Maybe both sides even claim that their opposing revisions are verifiable (e.g., conflicting information from ostensibly reliable sources).
This already happens, of course, and all too regularly. There are plenty of solutions: a central editorial authority, perhaps, or the tried-and-sometimes-true method of finding consensus.
Now let's drop the assumption that everyone would contribute in good faith. Vandals, trolls, spammers, and more all threaten the integrity of factual information. Sure, some of this would, through blocking and recent changes patrol, be undone by other editors, and pages would again reach a sort of equilibrium. But more insidious, subtle untruths introduced into articles, such as the Seigenthaler incident, might lie undetected for weeks, months, and years.
But what if we started contacting the subjects of articles—assuming no one tries to perpetuate a lie in an article about, say, limestone or cheeseburgers—to help determine if any inaccurate edits have been made? Precautions should be taken to ensure that articles don't solely reflect the views of PR personnel, but wouldn't engaging the subjects of articles simply be an additional step in harnessing the sum of human knowledge? After all, over 7 billion people live on this planet, but only a fraction of them contribute or have contributed information to Wikipedia. Why not reach out to the non-editors to see what knowledge they can add? Even if they don't edit articles themselves, they can still be invaluable resources.
And again, after a certain time, most articles will have reached a sort of encyclopedic equilibrium. (I use the term "encyclopedic" loosely, as plenty of Wikipedia articles would not be found in any encyclopedia of the traditional sense.) At this point, no more substantial additions or changes would be necessary for an article to provide comprehensive general information, if you understand the oxymoron there, so pages could be placed under some level of protection or pending changes.
What would it take to make Wikipedia the true expression of the sum of human knowledge? Maybe it starts with allowing anyone to add any information.