Double stud wall without space between them – GreenBuildingAdvisor

I am starting a rot remediation project where the exterior walls of the house are as follows (from exterior to interior)

1. ~4inch veneer stone, on a supported concrete shelf

2. 1/2 inch plywood sheathing

3. 2×6, 24OC studs 

4. fiberglass batts

5. 6mil poly barrier

6. sheetrock

The veneer is being removed because of the lack of propery drainage and moisture management.

As we look at it without the stone, I wonder if there is an opportunity to boost R value by framing up a 2×4, 16OC studded wall on the shelf in front of the existing sheathing. Fill the 2×4 cavities with Rockwool, and tape all of the sheathing. The current plan is to sheath with LP Weather Logic and finish with some LP siding.

My question/concern of course is to ensure I don’t create a moisture problem. I would appreciate any guidance and input.