Best practices for redeploying WCP applications while preserving customizations?

I'm working to automate the redeployment of our WebCenter Portal-based application.  Our goal is minimal to zero downtime.

Because of potential ongoing page/structure changes I don't think we can reliably promote an MDS label after deploying the updated application because of potential data-loss for new elements introduced through the updated app.  Am I correct?

If we export the customizations then import it seems we have a condition where the remaining, unexpired sessions on the previous deployment version may make changes that are not captured in the export. Additionally we risk losing/overwriting changes made in the new deployment when importing data from the previous version.  True here as well?