Updated 2nd post with what I was up to...
Basically, I have finished the Peasant unit chain and now working on the Ashigaru chain.
Once done with getting these two unit castes working in a single province then it will be just a lot of Find/Replace work in TSV files to carbon copy them for each province in the game.
After that, each unit caste roster will be tweaked for stats and such then I might release them for play-testing while I work on the Samurai, Hatamoto and Kashindan unit rosters.
The speed at which I can release a Beta test of this mod will greatly depend upon the input I get from all of you!