IIS WebDeploy Export Server Package via Powershell
I can't see a great way of doing this with just PowerShell cmdlets. What I would suggest is using PowerShell to call appcmd to export the application settings and then grab a copy of the files used. Then I'd throw these in an S3 bucket, also through PowerShell.
Are you using anything to build the artifacts (ie: bamboo or teamcity?) If straight from VisualStudio use the AWS ToolKit: http://aws.amazon.com/visualstudio/
For deploys: I would focus on getting the artifacts pushed to S3 in some automated fashion (if at all possible). Once you get the artifacts in S3, work on your plan to use those artifacts again. Are they for bootstrapping new instances/servers from S3? Are they backups for DR purposes?
For example, we build using Bamboo and within Bamboo we can create a deployment plan with Tasks to execute. One of these includes uploading to S3.
**Checkout the following powershell cmdlets:http://www.iis.net/learn/publish/using-web-deploy/web-deploy-powershell-cmdlets