Comment 1 for bug 284899

Separating in repositories does have advantages I think.

1. The distribution of choice is selected by adding and prioritizing the repositories correctly, not by knowing exactly what the package names are.
2. After adding a repo, everything else will still "just work"; yum install mysql-server, yum groupinstall "MySQL Database".

You could for example add the repo already in the kickstart phase, simply by doing that and having the packages Provides/Obsoletes: mysql-server, you will get either CentOS-Base / OurDelta-Base / OurDelta-Testing.

Alot of this is a matter of taste I guess. I suggest discussing and testing before making too many changes to the structure at the moment.