This sounds an awful lot like ReBrick, only run by some kind of bot that would search through and index the MOCs from the rest of the Internet automatically. The last part would be very hard to do, and honestly I don't think it'd be that useful. As great as MOCs are, unless it's something spectacular there's not a WHOLE lot of reason to dig back more than a year or two or three in your search; odds are, someone's already done something similar to the MOC you're looking for, and has likely improved upon the original design a little, too. The most valuable part about old MOCs--the thought process behind using different techniques and such, especially when the builder had to figure out a custom-built solution to a problem that was solved with the release of a new brick--would tend to be lost in a YouTube/ReBrick-esque format. I love the old MOCs I stumble across here, because often there is dicsussion about technique and design style and process; the forum setup allows for and encourages such discussion, while the format you describe would focus on the "latest and greatest." That's not a bad thing, but it makes the usefulness of cataloguing hundreds of thousands of old MOCs minimal.