It has been a while.
After the last failure, work (and school) showed up in force. I did not have much time for Tangent, or more interesting things for that matter. But now work has died down, as has class. I've (finally) picked up the Dragon Book, and realized that much of what I was doing with Tangent types was very similar to the use of non-terminals in formal grammars. I asked a question about it on StackExchange, which... didn't really go as hoped. Though it did remind me of the vast gap between professionals and academics.
Which in turn provided a bit of motivation to get off my ass and figure things out on my own. So I've started in on yet another version of Tangent - this time on GitHub. And this time, the approach will be to have an exceptionally minimal end-to-end implementation that is built upon. First step is do enough to declare symbols, declare (unary) functions, parse expressions using the type info, and debug-print symbols. No subtyping. No records. No type operators. No strings, no ints, no bools.
Just enough to implement the core extensible syntax successfully. Don't get fancy. Don't get greedy.