Interior vapor barrier

We're building a house in zone 7a in Canada . We're considering using a smart vapor retarder rather than a 6mil poly sheet on the inside of the wall. We will have 2 inches of Rockwood on the exterior and 6 inches of fiberglass on the interior.

This may be a stupid question, in the interest of saving money could I use poly on the top portion of the wall and the smart vapor retarder on the bottom 1/4. This way if there was a huge hole/accident causing extra moisture it would still be able to dry out? The materials would be sealed together and air tight.