The passerby whose hat falls off in Eastwood is The CourierSince it's become fairly obvious, or at least largely accepted, that the town of Eastwood is actually the Divide before its destruction, it's not exactly a stretch to assume that the man in the duster that Twig bumps into is actually the Courier, maybe on his first run through the Divide, that sets off the events of Lonesome Road, and Ulysses' Start of Darkness.
Why was the the Mysterious Stranger carrying that box through Eastwood.
The NCR Veteran Ranger is a descendant of BenSince the info he provides seems to be Ben's full name, and the ring is how he says he knows who Ben is, it's more than likely he shares something personal with Ben's family from before the bombs dropped. Given how long ago that was, it's either a debt somebody owed Ben, or Ben fathered a kid before everything went to hell, and now a descendant is looking out for his forefather.
The background of Vaults 7 and 10 will become Ascended Fanon, with a slightly higher chance for 7.Because A) they fit the Fallout universe so damn perfectly, and B) Bethesda and Obsidian both have shown that they love the series.