A suggestion that would be easier and cheaper when building a house would be it use 2x6s for the outside of the frame and alternating 2X4s for the supports. The blue bar is the 2x6 and the red are the 2x4s.
I was thinking of doing this when building a house for some of the interior walls to reduce the penetration ability of sound by removing direct transfer from drywall to 2X4 to drywall. Using it for the exterior would do the same and allow for extra insulation, it will not be as good as one foot of space but gives and extra 2".
Also, I would not use MDF in a home as it gases off toxic chemicals and if it gets wet it swells and falls apart.