Regarding memory management, the beauty of it is that the texture tends to use only the characters that are in use at a given moment. That is, suppose you have a font texture that holds a lot of 72px characters because you are showing a splashscreen GUI, for instance, next when you move on to another screen, like for instance an inventory menu, if you start using smaller characters of the same font, say 16px for titles and 12px for subtitles, whenever the texture is full it will be rebuilt, but without the 72px characters since they are nolonger in use on screen.
I've got my own integration mostly working and I am happy to share it too for free. At first I considered putting a price on it, but I'm happy to share it freely as every one seems excited about this. As long as I don't have to answer zillions of questions about it, I'm happy to share.
Eventually, ArenMook, I really think you should get down to integrating this in NGUI. It's not a lot of code, and what worries me about my own solution or any solution I could pick up on this forum is maintainance --> since I basically modified some of your source code, everytime you submit an update in assetstore, it's still going to be a bit clumsy to apply my patch on top of it.