I've initiated two discussions at hubFS (Post 3806 and Post 3786) on some aspects on znPlugin. Specifically, the parts that relate to performing efficient type comparisons and casting. There are a lot of ideas in that thread, including some sample code. Post #3875 is particularly significant, as it is responsible for the latest changes in the framework.
The discussions have slowed somewhat, but they are still good reads for people interested in Reflection within F#.