Whether he goes heavy with bags or trailer, or ultralight with bags, he needs much lower gearing to get any gear over the mountains.Many thousands of cyclists who ride the mountains every day with standard road bike gearing might disagree. If the load is light and the rider is fit, standard gearing is fine. Given the option, my preference is low gearing too, but it's not a requirement in all situations.
Even pros (super strong amateurs) go with 39x27 or a compact crank with 34 ring when they ride the mountains. So non pros probably need quite a bit lower to get up a mountain. Especially if carrying any baggage. I've met cyclists who use 39x32 gearing in the Rockies. Unloaded. Add 10-15 pounds of bags and I'm doubtful many can make it without at least 39x32 or 34x32 gearing. The Rockies are sort of easy in grade compared to the Appalachians.