Ubuntu live cd customization - part 2

Hey, quite a while back I had posted a thread on how to create a customized ubuntu iso. I had already used the guide here. Like before, I used that guide and successfully made a custom iso to put on a USB thumb drive. It works just fine. The problem is, there are certain things I want to customize, such as the theme, numlock, firefox settings and bookmarks, file management properties, and the like, and I cannot find any way to customize them through the terminal (which is what I'd have to do when making the custom iso, or finding the settings files to edit manually).
Rodster before had suggested I try persistent mode. I gave that a try last night, but after I got the settings the way I wanted, I wanted the thumb drive to be read-only. I moved the switch to read-only mode, and it will NOT boot up properly. But if it's set to read-write mode, it works fine. I'd get errors such as "can not mount /dev/loop1 on /cow".
I researched it last night, and it appears it is NOT a bug in my particular scenario, as the persistent file needs read-write access, and there is no workaround that I can find.
The only thing I am left with, is this. But that would require unsquashing the casper-rw file, and extracting and moving the contents over to a customized iso. Can anyone give me some advice? I'd be very grateful as always .

 

I'm not surprised nobody knows. It starts getting complicated when I have to decompress the casper-rw file, extract contents, etc. I've been thinking about this issue some more, and the only thing I can come up with is, it would have to be redesigned in a way that lets you save changes, and then lets you somehow "lock" the file to prevent further changes, thus allowing you to switch to read-only mode for thumb drives that support it. So I guess I'll just have to keep doing it the hard way.