Once you’re into shared storage, in my opinion, you should abandon the notion of using a “capture scratch” folder. In our shop, the SAN has NO capture scratch folders. Rather, the footage is digitized locally over multiple systems, then moved to appropriate folders at the finder level, organized by show, date, type of material (interview, b-roll, etc.).
So, to answer your question, I’d suggest that you have separate “elements” folders that contain your perennial resources that you tap into over the year. That’s the beauty of X-SAN, and FCP. You can just use the basic Mac folder structure to organize your media.
It sounds like you really need to sit down and think about how your media will be organized. Take advantage of the fact that FCP can have multiple projects open simultaneously, and use that feature to separate the process of digitizing from how your media lives on the drives.
Good luck.
Mark