This is obviously not impossible, but we are now in the realm of adding clauses to an already rather specific scenario, each clause adding another degree of imp

This is obviously not impossible, but we are now in the realm of adding clauses to an already rather specific scenario, each clause adding another degree of improbability. (The odds of "an upload cult arises on a planet" is by definition greater than "an upload cult arises on a planet AND actively presents anybody else on the planet from ever leaving.) I think the metaphor to look to isn't necessarily even human civilizations spreading around the globe; it's life spreading through the planet to colonize every niche out of which the slightest scrap of energy can be extracted.