The Morrow Project was/is a post apocalyptic game with the conceit that in 1962 a mysterious (and quite likely psionic) man named Bruce Edward Morrowrecruited nine leading industrialists and formed something called the Council of Tomorrow and predicted (with evidence acquired via his temporal teleportation abilities) that an apocolyptic nuclear war was going to happen. So they came up a plan to survive the war and rebuild in order to preserve the human race. This plan involved setting up caches filled with advanced (future) technology and cyrogentically frozen personel, and a large base housing 150 un-frozen people who were the leaders and organizers. World War III started on November 18, 1989 because of a computer error at NORAD. Afterwards the Project Leaders started rebuilding, but were attacked and destroyed by a madman only known as Krell. One hundred and fifty yearts later the damaged computer at Prime Base sends the wake up call and the players find themselves in a future where the war is all but legend.
Essentially, have the Hoffman Institute set up an insurance policy for the Final War, Project Bolthole. Personnel (a mix of combat trained, scientists, medical, agricultural experts, engineers, whatever) were placed in suspended animation in prepared sites with all the equipment they would theoretically need to assist in rebuilding after the war. The Institute itself doesn't really survive the Final War (because it was part of their enemies' plan and the Institute's facilities, including Prime Base, were must destroy targets. The remnants form the Hoffman Legacy and somehow carry on, but have no knowledge of Project Bolthole so it's never activated. Centuries later some deus ex machina causes the wake up call to go out to the boltholes, or maybe just to the players (or the one the players will be interacting with), dumping a pile of people from before the war with the most advanced equiment the Hoffman Institute could supply, some of which was in advance of their usual high tech wizardry. The bolthole occupants find a world were the Last War is all but a legend, populated by horrible monsters, semi-openly controlled by the enemies the Institute was fighting. They have to survive and try and rebuild. They pledged themselves to save humanity however they could, but they're alone and facing a job intended for thousands with careful coordination. Then there's these crazy warrior monks and tech-priests calling themselves the Hoffman Legacy.
EDIT:
I felt I should clarify this. This idea isn't about giving the PCs tons of cool toys and then letting them conquer Gamma Terra. It's about them facing an impossible job with no support. Their bolthole was stocked with a reliable vehicle, equipment and supplies for a few month to a year, with a large, but not finite supply of power cells, ammunition, etc. They have maps and records that will tell them where other boltholes and caches should be, but it's been a long time since that was all set up. I good way to put some impetus to their need ot go get more stuff might be that instead of a wake-up call, the bolthole woke them up because it's fusion generator is running out of fuel or otherwise failing. It might give them power for few days or weeks after waking them, but after that they're down to solar chargers and whatever they can scavenge.