Those are some interesting ideas, but the part about the souls is somewhat speculation, so we should try to find Grimoire cards to back this up. It's been proven that the Traveler did visit and abandon the Fallen, and its past with the Hive is seen in the Book of Sorrows Grimoire collection. Basically, the Traveler and other beings/machines of the "Light" attempted to destroy every living creature on the Hive species' homeworld, in order to destroy the "Darkness," a species of worms (similar to the worms seen on the Dreadnaught). The Hive species ended up making a deal with the worms to combine as a species and create the Hive we know of. Of course, they proceeded to exterminate every other species on the planet and leave the system. Therefore, I think the "Light" is just as evil as the "Darkness" in this case. I'm not sure how the Vex fit in yet, but the "Darkness" we destroyed in the Black Garden doesn't seem to have any connection to the Hive's "Darkness," at least not yet.