Wall assembly risk factor – GreenBuildingAdvisor

A similar question to this has been asked before here https://www.greenbuildingadvisor.com/question/modified-perfect-wall-what-happens.  

I realize this is not the perfect wall and either is the one described below.

The building climate zone is 6 (Prince Edward Island Canada).  The wall assembly is from inside to outside, latex paint, 1/2″ sheetrock, polyethylene vapor/air barrier, 2X6 16″ oc wood framing with unfaced fiberglass batt insulation in the cavity bays, ZipR6 with taped joints, vinyl siding.

My son in law is proposing this wall construction and I believe it to be a risky (how risky?) wall so I am looking for confirmation either way.  He has received the building code permit and is getting ready to build.  

My reason to consider the wall risky is the following.  The poly is a difficult air barrier to get perfect.  Any air leakage has a chance of condensing on the polyiso (I believe it is polyiso?) of the zipr if it is below the dewpoint.  My understanding is that the minimum insulation thickness (from Martin Holliday’s https://www.greenbuildingadvisor.com/article/calculating-the-minimum-thickness-of-rigid-foam-sheathing) is R11.25, and “should be?” exterior to the sheathing.  I am also concerned that any air that reaches the ZipR can migrate through the foam insulation at the cracks and condense on the tape, being absorbed by the edge of the sheathing.  I understand the one 4′ side and one 8′ side of the ZipR is extended so there is not a gap in the foam insulation but I do not believe this is intended to be the air barrier otherwise why tape the OSB seams?  I am also concerned about drying potential.  The OSB can dry to the exterior  but the I believe the Polyiso would have a low drying potential to the exterior (I can’t seem to find the specs on the perm rating but according to this BSC article https://buildingscience.com/documents/guides-and-manuals/gm-guide-insulating-sheathing/view  polyiso is 2.77-4.49 so is Vapor semi-permeable Class III vapor retarder so some drying potential)  and the poly vapor/air barrier would have no drying potential to the interior.

I will also add that they will be using heat pumps for heating and cooling and there is more and more air conditioning (cooling) being used here in the summer.

Thanks for any advice