as my seemingly endless research continues for best bang for buck wall structure, I am leaning heavily on a staggered stud 2x4 walls.
The idea would be 2x4 on a 24" oc spacing both inside and outside, with a 12" offset. I would use 2x8 plates, filling the void with cellulose. This puts a bearing stud every 12" oc.  However it makes my exterior sheathing attachment points and interior gyp points at 24" oc.  I would then use a exterior sheathing of probably 1.5" XPS with no osb except for where required for shear (which will actually be about 70% of the wall surface).  At these locations I would drop down to 1" xps.  Would I be better off just sheathing the entire thing and using 1-1.5" over the entire house?

The reason I am leaning on 1.5 instead of 2 or more is because of the attachments.  I will use 1/2" osb strapping drainage plane, but if I keep it to 1.5" I can sheet them using 3.5" nails with my gun instead of using 4" screws every 6-8" (if using thicker foam).  This will still get me a pretty decent R with very low infiltration.  Sheathing (both foam and osb) would be set in caulk prior to attachment, as would bottom and top plates.

Even though I am using 2x8 plates, and 2x4 24" oc, this still prices out to be slightly cheaper then 2x6 even at 24" centers, plus a little higher R.

I have a 3 stud jamb detail made with 1/2" osb window bucks that extends to the exterior face of the foam, giving full wood support under the window. 2 studs forming king and jack on the outer face of the window, single stud on the inner face.  The header would be a split box style header sized per the opening span with the 4.25" void filled with spray foam. Windows would be mounted set in caulk over the foam using 3" screws. 

so the question is:  Has anyone done a staggered stud framing before?  I have done plenty of 2x4 and 2x6 walls, never staggered.  Any issues that came up that had to be dealt with?  I have the luxury of time and drafting a framing plan and stud layout in Revit so I know exactly how much material it will use and also the layout & details to hopefully avoid infield issues. 

Also is 24" centers too far for 1.5" XPS or 1/2" gyp?  I have read conflicting reviews on 24" and 1/2" gyp.  Some think its just fine, others suggest using 5/8".  I personally hate using 5/8".

I'm also interested in this building method. I have a woodshop to build that I would like to experiment with using alternative building methods that "yet" fall under the purvey of traditional or "conventional" framing. That way I don't have to live in the space forever unhappily. Not trying to hijack the thread, but anybody with experience with these double stud walls find them difficult to get past county building depts.?