RHUM is an easy to use script for merging updated RPMs into a RedHat style distribution. RHUM can merge RedHat's RPM Updates and your own custom RPMs into the copy of RedHat you use for Kickstart installs, eliminating the need to apply RPM Updates after install. This script can also use Fedora Core has a base for building custom distributions.
RHUM has not yet been updated to work with changes in Fedora FC3. Jessie sends this workaround you can refer to in the meantime to help you out.
You will need to have anaconda-runtime RPM installed.
Some people may find this script helpful for building a network installable base from the yarrow images. If run in the same directory as the images, it will merge them into one directory.
If you make any fixes or add any features, send them my way.