One thought I had was to use the CD archived JPGs for each event that I use to put up on the website and for copyright submission in a third directory structure: 1 - RAW; 2 - DRV; 3 - WCR. The WCR directory would have subdirectories (event name) with the relevant yyyymmdd-hhmmss.jpg files under it. Would it make sense then (and is it possible) to rename files in the RAW and DRV directories to sequence names and keep the yyyymmdd-hhmmss name in metadata. Alternatively, since the data Photo Mechanic originally used was in the metadata anyway (i.e., Photo Mechanic could reconstruct it) could I just keyword/tag by the filename.
Why do you want to rename? I don't see the benefit. If you like the way you are doing it, then keep this system, It generates unique names and lines up in order. There are several ways to put the old name in metadata, but I'm not sure why you would want to do it.
If you want to go to a new naming structure, maybe Jan1, 2006 would be a good time to switch.
Rather than trying to use the Web Galleries as a content guide, I strongly suggest DAM software to do that. Use Catalog Sets or Keywords to keep the material organized by subject. I do keep my web galleries in a separate directory (actually, they all fit in one bucket. It takes a long time to make 4 gigs of web galleries.)
And keep in mind one of my main rules. Get the new system up and running before you try to tackle the old stuff. It will all become more clear once you have started using DAM software and feel comfortable with the new system.