Update:
The first pass implementation of NZFS's IO system is now complete.
I have also completed the RAID engines. Some were ported and adapted from FlexRAID's RAID-F, and others were built from scratch.
There is an advanced layer that still needs to be implemented, but I will get back to it later after testing the basic concepts.
Next step: OS integration (platform specific stuffs - after this, I will have a real storage pool to play and test with).