We are working on the upcoming release of PwnageTool 1.2.

One of new features will allow you to add Installer.app packages that are obtained from existing Installer repositories, you’ll be able to just add these into PwnageTool and the packages will be automatically added to the custom created .ipsw.

We thank the RipDev team for the help with this, they are really helping us to bring this feature from the Installer.app side.