[Mike McPherson] “shot in a myriad of formats: REDCODE, XDCAM EX, DVCPRO HD and H.264 (from 5Ds and 7Ds) just to name a few.”
All I can say is “Good Luck”!
There is hope however. If you keep all the full rez material available and on-line, then your “up rez” is simply a “Reconnect” rather than a redigitize. This is INFINITELY easier and faster than redigitizing all of your material.
If I understand correctly, your issue is not storage size, but throughput. Therefore, down rez (using compressor) all of your original material to the lowest acceptable codec for editorial that you can stand. We use Off-line RT HD. It looks like crap, but we can view almost unlimited multicams (regularly use up to 14 angles), the rendering is quick, and the storage used is small. The downside is that the frame size (pixel count) is smaller than the original frame so grfx, stills, text must be repositioned upon uprez.
In your case, PROres proxy is probably the best choice.
Once you’ve downrezzed, HIDE the original full rez media from FCP. Either dismount the volume, or disable access… however you choose to do it, make sure that for editorial, you’re NOT referencing that material. Edit with the low rez stuff, and then when you’re done, simply do a reconnect to the high rez.
Note: for this process to work smoothly, do NOT rename any of your clips.
Mark