So I've gone through all my sources and, well, I learned a lot. Stuff I've never known before. I've known how to write hiragana and katakana for 15 years now and I picked up a lot of stuff I never knew. For example; diphthongs, voiced and voiceless consonants, mora, nigori, sokuon. And you know what? I learned how to write perfectly fine without ever learning those things.
Most of the things I picked up in my research are words that linguists use. This, in my opinion, is a problem. When I was learning Japanese I was taught that the word 'desu' is a copula. Since I was in high school I just glazed over the information. When I started teaching, I suddenly wanted to know what it was. A copula is a word used to link subject and predicate. Yeah, that's not a whole ton more useful. So what I'm planning on with Japanese Arena: Kana is to keep everything as simple as possible. Avoid using words that could confuse the user and replace it with something easier to understand. Heck, I had students that didn't know what a verb was. I'm going to do my best to clarify all new words.
But on the other hand, I am trying to make the single thing that anyone should ever need to learn all there is to hiragana and katakana. So after they've gone through and learned how to write everything, I'm going to add a few extra, optional lessons to cover advanced terminology.