I've seen that Mac Drive 7 adds HFS+ and HFS support to windows for both hard-drives and CDs, which includes handling problems like the mac partition format. Clearly that must mean that file system support in windows is extensible somehow, even if it is slow. So where could someone start to write a simple (or not) file system driver for windows? I'm having a lot of trouble googling for this because these are commonly used words.
You need the Windows Driver Kit (WDK). The Installable File System Kit which is part of the WDK should get you started.
Good luck!