in case if you didn't knew, few days ago a mod that is called Call of Chernobyl has been released,
what mod is it? is a mod that has about 32 Explorable maps, including Dead City, Darkscape, Generators, etc, it also has a custom map called Trucks Cemetery, the mod is Free Play and i think there are some repeatable tasks.
the mod is here
by the way, the mod is for S.T.A.L.K.E.R.: Call of Pripyat.