It's a pretty interesting idea, and actually really well thought out I can see from all the details. I'm not sure how easily they could incorporate some of the ideas/limitations and such between these people and how it would affect them and the rest of the world around them, but FFXIV does it all the time with the phasing element of Fates, so I'm guessing it is possible, but it all depends how much they would have to alter their world to create that kind of thing. One other thing is since they said all of the guardians are working together, they'd have to incorporate some kind of element in the story, like they do with the crucible, how this is some form of 'training scenario/challenge', but that really shouldn't be that hard to do. The cool thing is it has pretty much infinite replay-ability (like the crucible) because you would be challenged by a living mind, rather than NPCs, of which patterns and strategies can finally be memorized.