I know that some people say that you cant go wrong with Bach. And while I agree, I tend to think that if you want to play Chopin Etudes, then practice Chopin Etudes. Or atleast the preludes. Im quite sure that practicing the WTC would help greatly in passage work. But really, it seems like rather a long way 'around the block' to me if you are trying to use it purely as a stepping stone.
That said, if you like Bach and want to learn his works then Im sure it will have additional benefits, advancing your basical technique.
With respects to 10/4 and 25/2...
I must admit that the passage work is what messes me up with both of these pieces (as its intended to, Im sure!). Again, Im sure that playing some of the fast and fiddly Bach would help, but personally, if I wanted to do these particularly pieces Id prefer to spend my time on Chopin. Id work through his preludes while learning the etudes. Infact, thats what I am doing! I cant play any of the etudes adequately yet, but Im finding that the more I work on these pieces, the more I study them, the more familiar they become (musicially and technically) and better I fin equiped I find myself to deal with them.
Not sure if that helps you at all.
SJ