Don't give up on Reese yet, the exchange between Neil and Reese outside of the elevator as Reese is leaving foreshadows a deal between those two. Reese calling him a son of a bitch but their best damn son of a bitch and Neil having the familiarity of calling him Reese. These two have worked something out together to defeat T. Pratt.

And yes the arch model would have taken weeks to build and just doing a peer review of the design to check it wouldn't fall down would take more time than Reese allotted but hey this story requires a willful suspension of reality. PS cleanest job site ever that they met on.