[AlexanderHowl]

Since WWII technology depended on fossil fuels and there would likely not be any fossil fuels on a Ringworld, they would collapse back to the technology of the 1860s (when everything could depend on wood as fuel). Unless humans were divided into village-sized units and provided with food until the first crop, the majority of humans would starve to death. I can imagine a scenario where a well meaning but clueless alien civilization accidentally kills 90% of humanity in an effort to save them from the horrors of war by transporting them to a Ringworld and leaving them to starve to death because they did not think to leave sufficient supplies.

The resulting loci of human beings would probably not have any contact with each other because they could not travel the vast distances involved. If we assume that the aliens clumped humans together in groups of one million people, they would have created 2,300 loci of humanity (before the resulting kill off from mass starvation if the aliens were clueless). With an area of 3 million Earths, the distance between the center of each loci would be around 900,000 kilometers, over twice the distance of the Earth to the Moon. The Cardiff locus might as well be on another planet than East London locus because no one would travel between the two on foot or on boat.

Now, this is not saying that it is a bad idea, it possesses a lot of gaming potential, it is just that the first generation after transportation would be quite difficult. I imagine that quite a few people would be interested in getting bloody revenge on the aliens for their imprisonment (and/or genocide) of humanity. Of course, it would require superscience, but I do not think that is a particular problem with the idea.