Nick, the formulas at the URL you posted are close but do not match those in the C41 and RA4 solutions.

In particular, the film 'blix' is low in ferric edta even for a bleach, and will not do an effective job of removing silver. A key interimage control ingredient is missing from the film color developer.

The paper developer is missing some ingredients as well.

They may work just fine, but why take a chance. The actual formulas have been published in the patent literature. I'm surprised that no one has just taken them and tested them and then published them. That would solve all of the doubt.

Even then, I would still buy the stuff ready made in kits. It really saves a lot of hassle.