You know what I want? A Fallout RTS and Civilization sim. Set before, during, and after the events of Fallout 3 you command the Brotherhood in their war against the Enclave and Supermutants across the Capital Wastes.
Resources would include Caps, Scrap, Hides, Energy, Food, Water, and other necessities of the wasteland. Other resources would be the locals, who can be recruited, trained into initiates, equipped, and deployed into the wastes on a variety of missions. Robots can be repaired for even more firepower. Wildlife like Molerats and Brahmin can often be domesticated, or tamed if raised from a young age like Deathclaws or Yao Guai.
I'd make the entire Capital Waste playable, with various factions like local raider gangs, Tenpenny Tower, Underworld, The Outcasts, all sorts of people to interact with in various ways. Maybe the Brotherhood at one point takes Tenpenny Tower as a garrison. Perhaps there's a campaign against the raiders of Evergreen Mills. And even before then there'd be a whole chapter of the game about the scourging of the Pitt.
The whole thing would only be semi-canon, but it'd be fun. It'd be a nice look at the events around that time. Plus there's a lot of potential for interesting gameplay as you have to manage scavenging teams, secure various locations, arrange water caravans. Could be extremely fun.
But Bethesda would never do it.