You can use the K setting all in-camera. However, I played with it early on when I got the 1Ds, and found it to be too cumbersome to use in real life (I even had a color light meter). It may be great in a studio, but outdoors it's just not practical. Plus, it won't help with the color cast too much.
If you use raw, you solve the problem. As for disk space: a 500GB drive is $250 today (or less). It takes my card reader (Lexar Pro FW) 13 minutes to download a 8GB flash card. I can put 400 1Ds2 raw+S images onto one of these cards, so you should be able to put 800 1Ds raw-only files on one. That makes 100 raw/GB. That makes 50,000 images on one $250 500GB drive. I don't know how much you shoot, but that would last me about 18 months - not too much money if you ask me.