Tool or procedure for creating updated installation ISOs

I am interested in finding a tool for updating baseline isos with all the current updates.

We currently install the baseline and then do a massive yum update. I'd prefer to occasionally create a custom iso with all the current updates relative to whatever RHEL version it is. I've figured out some scripting to do most of this but because I have to use RedHat Satellite I've not found a way to get a listing of updates without having a baseline actually installed.

Is there such a tool?

Mark