Make the outside world like Fallout 1/2. The more secure you build your base/factory the further out you can travel. Perhaps just start by adding small, and I mean small, towns (maybe they have gangs) and grow from there. Perhaps you can only get there by train.

I believe the suggestion is to be careful.

Personally I like the water unlimited because it in a sense regulates itself. Rain would replenish hence no need to have the drain and refill process. THOUGH adding actual rain to the game would justify the endless water.