How to create a Package, which runs a shell script?
Could you do this with Platypus? I use it to package small executables with a shell script into an install app, which uses the shell script to move executables into the target folder on run. You're still going to have issues with your intended result however as I can't see any way around running a package install without requiring admin access IF the package normally modifies files that require admin permission, but you should be able to put the package, the configuration file, and the install script together into one app using Platypus. End users can then run the app to install the package with your desired configuration.

The setup is really simple, the output is minimal. This is not a program designed to do anything complicated but it is free and has been really useful for distributing self-written script-based apps.