I'd love something similar to the Stronghold quest lines in Morrowind. Once you advanced enough in one of the great houses of Morrowind, you were given a quest to commision and build your very own little castle. Something like that would be very welcome, it'd give me something to sink all my fifty billion caps into.
Once you've got a budding little wasteland camp going, you could do more quests to upgrade it. Like getting a water purification system set up, for a reliable source of good water, or attracting merchants so you've got somewhere to flog your loot.
It can't be too difficult to do, would fit rather well with the theme and give you something to work for with all those caps. Once it's a well established little wasteland stronghold, perhaps the end reward could be a scrap metal statue of your character. Little things like that.