How about the following idea: you bring the necessary contents to a NPC - a base builder/trapper first.
Then, you join his party with some other builders and he leads you to a possible "safe" area, like a trainman, where a base can be built. During that, you encounter critters as usual, and defend the NPCs at all costs. The direction is random - if you don't like the place, the Builder goes to the next random area.
If you want a quicker pace of things, you can help him to repair and refuel his truck, as a separate quest.
Arriving at the site, he will ask you to cover his and his workers back, as he saw some raiders following them. You start guarding the construction site, while the NPCs start working on the base. Some waves of raiders will arrive, which you have to defeat, while protecting the workers. The map will change between the waves, until the base is erected. The more workers you lose, the more waves you have to defeat.
If you have a character with high skill in your team, you can send him to help the workers. There is a way to procedually change the map without loading a new one. Technically, the changes will work, like animated doors.
So: To open the locked door, you need a lockpick set and high enough skill to open it.
And: To blow up a pile of with crumbling stones animation, you will need a dynamite and traps skill.
Or: To erect a girder, you will need rope and strength requirement.
The animation will turn to static scenery anyway, after the new map loaded after defeated wave or raiders.
So, instead of just paying the man, you get a quest to build your base.
Tell me what you think.