Purchase the fire wire drive that takes a CD/DVD and fit a HD caddy then you can swap your drives with cheap caddies, thus saving all those FW DRIVES. You will need to power down the drive when swapping so the system refreshes.
Just out of curiosity, what brand of HD caddy and Firewire drive enclosure are you using? I tried this with an ADS Pyro drive and a Lian Li RH-322 caddy, and the Lian Li was too deep to fit correctly.
I use this setup as well and can thoroughly recommend it. I purchased my housing from a local retailer (in OZ) but I know they source this type of accessory from Anyware
Note that the photo is very misleading (read confusing) as it shows a graphic of the rear of the housing sitting on top of a graphic of the front of the housing!
I then bought an IDE mobile rack like - this and mounted it in the housing. I have two 20G drives mounted in drawers like - these that I can slide in and out as required!(after turning off the power to the external housing)
I did this with my ADS Pyro firewire enclosure. I use an "In Close" brand caddy, sold through Fry's electronics here on the west coast of the US.
I discovered that there was not quite enough room to fit the caddy inside the Pyro box. I had to do a wee bit of creative modification at the back of the box to make it fit, but now it does. Specifically:
(1) remove one of the four muffin fan screws and cut off the extreme corner of the muffin fan grille;
(2) gently bend the power connector mounted on the Pyro circuit board over to a 45 degree angle (no big deal, though you wouldn't want to bend it back and forth a dozen times, since that would probably make it fail);
(3) carefully fold the EIDE ribbon cable like an accordion in order that it can be made to fit in a very small space behind the caddy.
That's it. The In Close caddy fits in the Pyro box, and now I have the best of both worlds--large disk portability, and simple disk swapping.