The GECK is supposed to have a "replicator" in addition to the power source. It also has instructions for building a more permanent settlement from deconstructed vault systems, and sand.
The "two per vault" thing is weird. The computer in Vault 8 does say that, apparently. It's in the context of a bit of a joke - apparently Vault 13 was supposed to receive a whole box of water chips but got an extra GECK instead.
Which is weird since it should have had three... But after Fallout 1 the Vault Dweller leads a group out of Vault 13 and founds Arroyo. 80 years later they're worshiping the *idea* of a GECK, but they certainly never had one. They're kinda idiots to be honest, maybe the Enclave was on to something there.
Anyway, the "two per vault" statement only comes from the Vault 8 computer that I can tell. It's hard to explain, since all other evidence points to GECKs being rare as hell. I only know of three successfully used - Vault City, Arroyo post-FO2, and the *one* found (or ever mentioned!) in the Capital Wasteland.
I guess one could assume that all Western vaults did have two, but nearly all were wastefully looted and the instructions/seeds discarded. Heck maybe that's what those stationary "fission batteries" are, the big ones being used to power streetlights and such. No sign of the "replicators", but it's something.
Also radiation is very different in this setting than in reality. It's one reason everything is nuclear-powered. Heck, I don't think ghouls are a result of FEV... Just magic radiation doing weird nonsense. A lot of them were turned when the bombs dropped, long before the FEV started spreading. AFAIK.
Not really. The FEV spread when a bomb directly hit the West Tek research facility (later known as The Glow). Although it's somewhat disputed whether ghouls are a result of plain 50s pop-scifi radiation or radiation mixed with FEV. The latter makes more sense (and is stated as canonical in the Fallout Bible), but the former is what the original creator envisioned.
Huh interesting, thanks!
I definitely misremembered the fortification level of some of those FO3 towns. Some don't have the magic stop-anything rubble walls, and would be pretty vulnerable.