essentially the engineer would be like an RPG. you start of in a massive world mostly empty with a few settlements. you play as an engineer and your job is to well engineer things. you start of with basic tools and basic components. you have various quests such as building a bridge to support trade between two separate villages, building a house or building a massive weapon so the village is protected etc. you get money from doing these contracts which can be used to buy more tools and components. you can also just build something for the sheer hell of it or even build your own tools like a crane or dozer to make building easier
of course for a game like this to work it would need an excellent physics engine
of course for a game like this to work it would need an excellent physics engine