Well, it's not *easier* per se, but this could help you achieve what you want, ... sort of:
Go read and understand
http://www.nostockui.com/2010/03/mak...rface-sandbox/
Then just install the UI for the mage in one installation of WoW, and the UI for the Paladin in the other installation, and exit WoW completely and run the other copy of WoW for the other toon.
This is ... not the most convenient for sure. My advice is find a UI base that works for either toon (it's probably going to contain Clique and some kind of raid frame) and then just add in something to manage ports like
Lunar Sphere or
Broker Transit if you have an LDB display in your UI, and
Pally Power and disable it for all your toons, then enable it for just your Paladin. Voila, one UI for both toons!