It is either bug in how deployments are treated or how overlay/vfs work.

Steps to reproduce:
1. deploy undexploded war with jar inside
2. add overlay that will add non existing file in jar

Result: exception:
Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: JBAS018776: Failed to get content for deployment overlay WEB-INF/lib/overlayed.jar//META-INF/x/file.txt at WEB-INF/lib/overlayed.jar//META-INF/x/file.txt
Caused by: java.io.FileNotFoundException: /content/shell.war/WEB-INF/lib/overlayed.jar/META-INF/x/file.txt"}}
at org.jboss.as.test.integration.management.ManagementOperations.executeOperation(ManagementOperations.java:67)
at org.jboss.as.test.integration.management.ManagementOperations.executeOperation(ManagementOperations.java:37)
at org.jboss.as.test.integration.deployment.deploymentoverlay.jar.OverlayUtils.setupOverlay(OverlayUtils.java:76)
at org.jboss.as.test.integration.deployment.deploymentoverlay.war.OverlayNonExistingResourceTestCase.testOverlay(OverlayNonExistingResourceTestCase.java:67)

Expectation:
should work. It actually does work, if war is really exploded or
'if(exploded)' part in overlay is removed from overlay processor and everything is handled via: https://github.com/stuartwdouglas/wildfly-core/blob/a75af9118c4062fafb899b2c1109387a0748d925/server/src/main/java/org/jboss/as/server/deployment/DeploymentOverlayDeploymentUnitProcessor.java#L117

This is part of the fix of above issue, which depends on WFCORE-761.