terminal – Ability to add non-gui installer based plugins to pkg file

I’d like to have an installer that can run either from command line
installer -pkg ~/myInstaller.pkg -target /
Or in gui mode using open ~/myInstaller.pkg

However, I’ve added some installation plugins that are all derive from InstallerPane by default

#import <InstallerPlugins/InstallerPlugins.h>

@interface MyInstallerPane : InstallerPane

Perhaps there’s a way to write non-GUI based installer plugins that can also run in command-line mode?