Building a new home and am interested in adding a continuous insulation layer over the wall sheathing but have questions/concerns I can’t seem to get a straight answer on.

Home is in Zone 3, 2×6 exterior walls, R21 fiberglass, 1/2″ Advantech sheathing covered in mostly brick, some shake.
– Will adding 1/2″ Polyiso in lieu of housewrap “choke” the wall moisture. The Polyiso I’m looking at says it is allowable as a water barrier, but doesn’t seem like it would breathe like a house wrap.
– I like the idea of a continuous insulator for the thermal break over framing, and the foil side is a radiant barrier given the air gap behind the brick. Any drawback here?
– A downside is the windows will need the jams extended 1/2″
– So, does this sound worthwhile or just overkill?
– Any problem applying cedar shake over polyiso on sheathing?

Thanks in advance