Are you crazy man?! Everyone knows once you do that, they gain magical powers and are invincible! Just look at Graham!
But he was invincible before he was chucked into the canyon!
Nobody knows for sure. Seeing as you might have slaughtered everyone from the Crimson Caravan I doubt you'll be going with their caravan, so there might be a new Caravan company and merchant addition to the main wasteland. As for the DLC . . . Perhaps that Mormon missionary will have some goods, and if there is a friendly tribe they might have some.