Hi, my wife and I are building a tiny house on wheels in climate zone 6 (dry).  We have some size and weight limitations and the framing is cold-formed steel, so would the following wall structure work?

Working inside to outside:
1. Exposure 1 rated 19/32 plywood sheathing calked, air sealed, and then finished with drywall mud & high permeance paint. 
2. R13 fiberglass unfaced batts between the 16″ on-center steel studs. 
3. Benjamin Obdyke Hydrogap Drainwrap taped or glued to the outside of  the studs (for air sealing) with self-sealing tape (to prevent water intrustion from the cladding fasteners).  Open to be able to drain top and bottom.   
4. Two staggered overlapping layers of 1″ EPS type II foam board with taped joints.  
5. Corrugated metal siding screwed through foam sill-seal strips (for slight rain-screen furring), through the foam, and into the studs.

Would the plywood be permeable enough since there isn’t a lot of outward drying?  Should the drain-wrap go in a different spot?  Should I go with Rockwool batts to be safer moisture/mold wise than fiberglass?  Should I ensure a bigger rainscreen?  Any other ideas or should I just go with traditional exterior sheathing (with foam boards on the outside and interior drywall) and find weight loss options elsewhere?

Thanks!