I saw a video where as a stunt a residential construction crew went from a vacant lot to a complete single-family house ready to occupy in less than two days. And that wasn't a prefab house, it was a regular wooden frame suburban house built using all the usual construction methods. They did it by staging all the materials right there and having all of the carpenters, roofers, painters, electricians, plumbers, etc standing around ready to jump in as soon as they were needed. Granted that was a small project, but the point is that with a sense of urgency construction can proceed quickly, and it doesn't require sacrificing worker safety.