Maybe I'm misunderstanding, but you want to have a template come up with "default" audio already on the tracks? If this is the case, just save a project with the audio as your default project, and load and re-save it with a new name when working on new projects that require this same configuration and default audio.
I just figured that out. Thanks everyone for the reply >>> You know you need this when you do some intericate melody loops and don't want to remake them everytime.
Inserting a Project Template is the best of Reaper's features