I like to believe the Courier is actually a descendant of the Vault Dweller.
For starters, as we know from game chronology, Fo:NV takes place roughly twenty years from Fo2. That would make it likely the Courier to be the son/daughter of the Chosen One. Depending on how "active" the Chosen One was, the Courier likely being in their early twenties,
In Fo:NV available dialogue you can choose for your character, you can learn that:
During a conversation with Bruce Isaac in Novac, the Courier can state that they have been to New Reno before and attended one of his shows at the Shark Club.
Even if one has not made contact with the Brotherhood of Steel at Hidden Valley, the Courier can state they have heard of the Brotherhood when conversing with Veronica for the first time and, upon passing an Intelligence check, when interacting with Christine in Dead Money. The Courier may also be aware of their technology obsession and their hostility with the NCR.
According to Ulysses, the Courier has been to Circle Junction, New Reno, Vault City, Fort Abandon, and on brahmin drives at the Big Circle.
These bits of dialogue cues indicate the Courier is from, or at least visited, New California at some point.
Also, while I understand the Item Packs are entirely optional add-ons and not entirely canonical to the game... well most of the contents of the item packs can be explained as things that can be found throughout the wasteland so there can still be canonical explanation for most of the item packs... except for the Tribal Pack and the Classic Pack.
But what if the in-lore reasons for these Pack is that it consist of family heirlooms for the Courier?
The Tribal Pack could come from Arroyo, a post-war village founded by Vault 13 settlers who adopted a tribal way of life. Tribal Raiding armour could be based on the armour Arroyo warriors used to wear.
The Classic Pack could simply be family heirlooms that (depending when the DLC is active) the courier has on them when Doc Mitchell found them. The fact the Armored Vault 13 jumpsuit looks more worn than the vault jumpsuits found throughout the Mojave Wastelands shows the age and use of the jumpsuit.
At least, that's the theory I always had for Fo:NV Courier.