This is an interesting thought experiment, AllanS. I think something similar is at work when philosophers of religion like Craig and Plantinga invoke God’s “middle knowledge” so that God can see all possible worlds containing all of the various possible choices of free creatures. Of course, few (if any?) middle-knowledgers take a realist approach to the modal multiverse.
One interesting contention that the middle-knowledgers typically make, though, is that it is metaphysically possible that there is no possible world in which all people use their free world to continue willing the good only and never sin (in fact, the contention is that there is, in fact, no possible world in which anyone - besides Christ - lives her or his whole life without ever freely sinning). Plantinga calls this “transworld depravity,” and Craig attempts to utilize a similar notion to argue that there is no possible world in which everyone uses her or his free will to accept God’s salvific grace. Consequently, someone’s always gonna be in hell, and, for Craig, “some” means “most”! God knows all this through middle knowledge in eternity and chooses to actualize the (best? good enough?) possible world, despite the losses.
I think we can ask the same question about this example of an actual multiverse: whether, given unlimited worlds, we could ever hit upon a world in which a single individual freely chooses at every moment to make the morally correct decision. Your example seems plausible, since it is simple in its details. But what about a world (like ours) in which every single one of a vast majority of individuals must always freely choose correctly? The complexity of such a world would seem to imply that such a “perfect world” would be far more rare. That being said, given unlimited worlds, is this nevertheless metaphysically possible? It seems to me like there could. But, if it was, why didn’t God actualize that one?
Your experiment does have the interesting twist that the whole point is to get Frank to, at some point, continually freely choose the correct option so that the world isn’t annihilated. But you say that upon Frank’s choosing the correct blue pill, “God immediately annihilates the 999999.” The universalistic critique of an annihilationist eschatology might work here too: it’s all well and good that God gets God’s desired ends (a world in which Frank freely chooses the Blue pill and thus the continued existence of the world), but was it worth the cost of the thousands of worlds and Franks that were annihilated in the process? You say that “God is not about to take any chances,” but the fact seems to be that God did take a lot of chances, and almost all of those bets failed. It’s just that one didn’t.
Does this constitute a failure on God’s end to get what God wants? If God’s goal was just to get one such world, then it would seem not. But, is there reason to think that God would not want any worlds to end in annihilation? If so, then there would seem to be a problem. So, if there was something analogous to God’s universal salvific will for possible worlds, then it seems that the thought experiment runs into the same problem as the eschatalogical annihilationist. I think if there was to be such a principle, it would have to involve something like the consideration that since all those possible worlds are really real, there is real loss when each one is annihilated. The question would then perhaps come down to whether or not one thought that God’s end of one good world outweighed the loss of the thousands of others. Not sure how I fall with regards to that.
I’m just spit-balling here, though.