redistribute the combination. CentOS does a lot of work just to get to the point where redistribution is allowed and doesn't add much except an option kernel with more drivers included. I'd rather see that work go
And yum, which is a big change. You assume that Centos wants to do other stuff.
into something like a better installer, or combining newer desktop apps into the stable kernel/libs from RHEL - but nobody does because RH goes
I wouldn't recommend trying that too hard. Current gnome needs current gtk and really wants composite which really wants current X libraries and server which ... and so it goes on.
Alan