Air tightness is a critical step forward. I'm glad we are talking about it. Thinking more holistically, I would not go with the double-stud wall. You get lots of thermal bridging, and when it gets cold, your outer studs freeze. I know it's considered a straightforward system, but venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits. Let's build our homes for centuries, not decades, folks!