Had an idea for a Fallout mod one of these days
Sort of Fallout meets Buck Rodgers, in the sense that its the grimier, more "realistic" and "road warrior-ish" Fallout world turning into the world of vintage Rocketpunk sci-fi .
The world had its ups and downs in those thousand years (around 700 years after the latest games) but overall its on the way up - there's plenty of chaos, murderous mutants, warlords and general disorder, but overall the world is largely civilized again, even if in differing stages of civilization. The ecology has recovered somewhat, too, with some old niches being filled out by new mutant animals.
The player commands not X-COM, but the Brotherhood of Steel (they still exist). To be specific, a more open chapter that recruits outsiders. Its less of a chapter and more of a taskforce, because strange events that look like not of this earth cause many chapters (the Brotherhood is a mostly global force now, if small and splintered) decide to pool resources, despite divisions.
You can recruit two types of soldiers: Outsider recruits and Brotherhood initiates. Outsiders are worse, Initiates are best, but they're far more expensive.
Your taskforce is considered barely above laughing stock early on (lol aliens get real), so the early game is about following the breadcrumb trail and turning your odd force into something resembling fighting shape. Many people distrust the Brotherhood, so you have problems getting good guns - not as much as buying them, but getting them across national borders. So yes you're gonna have to start with spears and crossbows and 10mm pistols.
Early game enemies would be raiders, alien collaborators, mutant monsters, mobsters, warlords, etc.
To get the wasteland new governments to support you, you need to prove your power - so off you go to to fight all sorts of enemies for them. After all, they can't support you if they're fighting other menaces.
Main enemies would be aliens, but the Green Little Men and other more 40-50s sort of alien foes. Grays are more of a post fifties thing, or so it seems to me. Eventually you get fancy rocketships and take the fight to them across the solar system.
There are a lot more nations than in vanilla, because this world is more decentralized, but on the other hand its easier to lose nations as well. Rather than the vanilla diplomacy nations, you get a one-shot chance to stop a "Invasion" mission, but its a ultra-hard mission - think Terror Mission on steroids. When a nation is lost, it spawns further invasion nations from itself, using that nation's own forces - which despicts that subverted nation siding with the aliens and invading other nations for their allies/masters.
