The problems that [@catchamber]'s current proposal will run into are as follows:

The duplication of universes on the fly is going to turn people off, particularly people like me who have universes with incomprehensible amounts of lore behind them. The sci-fi world of [i]Stardust[/i] has more lore written for it than it does stories within it by an order of magnitude, and the unwritten lore is another order greater than the written. In no world could someone ever duplicate that. And if they did, it creates massive & abhorrent continuity errors. I would never subject [i]Stardust[/i] to that. The people that have these quantities of lore are going to be excellent worldbuilders that you absolutely want because they'll flesh out this infinite space. Yet the duplication concept is potentially alienating.

You have an infinite amount of space, made worse by employment of multiverse. I've run enough sci-fi groups to know that [i]everything goes to shit when multiverse theory comes into play.[/i] The fundamental rules of continuity are thrown out the window and that never ends well. It gets confusing very fast, leads to all kinds of potential powerplaying, godmodding, etc. Its quite literally and open door for godmodding because as you've described it, if the "local/thread GM" has said no, someone can simply duplicate that universe and go around them to get what they want.

The last major issue I'll harp on is that you have no way to bring players together, and your proposed system will actually encourage more fragmentation. At that point your persistent universe is really just a microcosm for the site as a whole, with the exception of overriding one of the accepted rules of RP etiquette. Unless you force players together, they will diverge. I speak from experience on that. I think [@The Harbinger of Ferocity] summed it up quite nicely. You need to drag players into involvement with a central plotline, or else they'll just go off and do their own thing with 1-2 others which IMO defeats the point.

How I would recommend proceeding is to treat it like you would any other large group roleplay on the site. Except, due to intent to run for perpetuity, you have very clear rules relating to ad-hoc player participation. It needs to be clear when and how players can jump in and drop out and precautions need to be put in place to avoid players becoming integral to progressing the plot, then dropping out/going inactive, and processes/penalties established for when it does inevitably happen. I believe based on my own firsthand experiences that doing anything else will be a recipe for failure.