You can add your scripts from your common project to the other projects using 'Add existing item'. Browse to the common project and add the file.
This will basically create a pointer for the file from the new project suite to the common project in a different suite. Although you can edit the file from the new project, it still actually resides in the common project.
From there, add //USEUNIT <FileNameFromCommonProject> to the top of a scripting file in the new project suite to allow access to the methods in the common script file.