I started a wiki page which documents the procedure for making an Ubuntu remix from scratch.
It works for my purposes, which is making a data recovery toolikt (http://rescubuntu.info/). In this case, it is easier and more flexible to start from scratch than to remaster an existing cd. Especially when the end-product must be console-only and run in very little ram.
The page needs work, so if anyone is interested jump in.
The page does not describe how to make the remixed live system use any graphical boot and the ubiquity installer is not tested out. Yet.