Description of problem: Anaconda makes it possible for a person who installs interactively to select additional repositories during the package selection. Unfortunatelly, this selection doesn't get reflected into generated kickstart file, and I have no idea if it is even possible to add repositories with kickstart. It would be nice it the only choice wouldn't be to install yum and then run it via %post.
Closing this, as I was told about "repo" kickstart option and seen bug 199468 and bug 206152.