I've been down a similar route recently. At the ends where I intended to interface with common air tools, I used common brass NPT adapters to mount Milton V style couplers. Not the absolute best for high flow, but I don't have the line losses to deal with, I do get noticeably higher flow when using V-couplers on both sides, and the more common standard Milton couplers I've been using for years also fit. Then for the real high flow needs (mainly sand blast cabinet) I use high flow 1/2" industrial couplers.