I thought I saw this mentioned somewhere, but I don't see it now. Anyhow, would this be feasible?
You use Add Media to add all your media to Project Assets. Then you create folders (Christmas, Thanksgiving, Birthdays, etc) in the Project Assets panel. You use the Trimmer to set the in and out points. You can CTRL-drag (or copy and paste) the corresponding clip in the Project Assets panel into the appropriate folder(s) -- thereby creating "subclips." While you can't drag from the Trimmer back to the Project Assets panel, you can drag the corresponding clip at the top level in the Project Assets panel to folders.
Note that if you try to create a copy by CTRL-dragging a clip to an empty square in Project Assets, nothing happens. But if you CTRL-drag a clip into a Project Assets folder, the "subclip" will copy to the folder. If you don't hold down the CTRL key, the clip is moved instead of copied. The copy will just be a reference to the source clip and includes the in and out points you have set in the Trimmer. You can also Copy and Paste from one folder to another.
Nothing so far has involved the Timeline. Everything is done in the Project Assets panel and the Trimmer. Nothing has been re-rendered.
Then you save the master Project, and make copies of the Project for the different genres. For each copied project, you drag the desired clips, such as from the Birthdays folder in the Project Assets panel, to the timeline.
I haven't practiced this, but it sounds like a great idea.