Overall, the process has been quite interesting. It is more or less forcing me to describe the design, which I haven't formally done before. Even though I know how it works, it is quite useful to read through the description and see what is really happening - it gives some feedback about what I need to be improving and where I will be extending the engine in the future.
The first half has been roughed in, and is added to the latest SVN repository commit on codeplex if you are interested in checking it out ahead of its completion. I hope to add in more detail, and add the second half within the next week or so, so more info will be coming shortly!