The te/ta-form is genuinely a separate system that doesn’t reduce further. I think there’s still value in having a solid model for everything else. At least I personally found it valuable, which is why I thought to share it with people.
I'm not totally sure this "stems and suffixes" mental model really works well for everything else. Forms like the imperative (食べろ), volitional (食べよう), provisional (食べれば), potential (食べられる), and causative (食べさせる) aren't cleanly handled either -- they work similarly for godan verbs, but you have to add a different suffix for ichidan verbs.
It's definitely useful to understand how "chi" and "tsu" fit into the hiragana chart, and if your asterisk notation helps you remember which verbs are ichidan vs godan then that's great, but I'm not sure it's worth trying to unify -masu and -nai into one model.
I'm not totally sure this "stems and suffixes" mental model really works well for everything else. Forms like the imperative (食べろ), volitional (食べよう), provisional (食べれば), potential (食べられる), and causative (食べさせる) aren't cleanly handled either -- they work similarly for godan verbs, but you have to add a different suffix for ichidan verbs.
It's definitely useful to understand how "chi" and "tsu" fit into the hiragana chart, and if your asterisk notation helps you remember which verbs are ichidan vs godan then that's great, but I'm not sure it's worth trying to unify -masu and -nai into one model.