EDIT: To have a quick and easy link-heap, the project documents are given below:
Sound changes from Proto-Japanese to Old Ifsume.
A basic wordlist.
Morphology of six-stem (equivalent to yodan) verbs; this bearing a great deal of resemblance to Old Japanese.
Coalescing the particles into nominals.
I've been gathering what resources I can find on Japonic linguistics for a project (a language for a work of fiction set in a world not our own; I'm simply not good at inventing roots and morphemes, and I find Japanese a very interesting and euphonous language), and have managed to gather the following sources:
Vowels
Verbs
Particles
For my own language, however, I find I desire to do the following: (1) have far fewer Sinitic borrowings; (2) produce native roots with initial voiced stops and /r/; (3) have present a phonemic /l/; (4) have such sequences as the frequent (C)yō, ō, (C)ya, ei &c. which appear chiefly in Sino-Japanese words, to occur naturally in the "modern" language that will resolve from the project, again without recourse to large-scale Sinitic borrowing; and (5) produce something of roughly equal euphonousness (to my ear) to modern Japanese, and complexity to Bungo, but to do so in such a way as very directly copies neither.
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As far as the desired imperative -/l/- form goes, I imagine it could be obtained from the */ju/ auxiliary used as a separate word, while where it fuses onto the word, it remains */ju/, leaving me with the -yu conjugation, which I desire to preserve.
In the interest of not having a very long post, I shall leave the current sound changes from Proto-Japanese here. Isn't that a rather cute font, too? I like it quite a lot — I found it going through the list of Japanese ones I had. I normally use Yu Mincho, but this one made me smile.
I do also very much like how Frellesvig reconstructs a vowel system that includes all of /i ɨ e ə u a o/, and will find such a reconstruction very useful to my ends.
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So the first stage of the language would look rather like this:
Nasal: /m n (ɴ)/ m n n
Stop: /p t k b d g/ p t k b d g
Fricative: /f v s̪ z̪ s̺ z̺ h/ f v s z s z h
Resonant: /l r w j/ l r w y
Vowel: /i e ɘ a o ɤ u/ i e ĕ a o ŏ u
A pitch accent will begin to emerge during this period, generally with words of two morae or less having a "flat" pitch very regularly (though the vowels /ɘ ɤ/ will frequently trigger a drop in pitch morpheme-internally); a few random examples from the Swadesh list, showing a few other sound changes in places: link to a more thorough document.
It is, admittedly, not as tidy as I might like, but it may be at least interesting, I hope.
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