I like the idea. Reminds me of a talk about syntax editor in racket but I forget what it was named. What languages can pantograph support?
The next phase of work is on instantiating more complicated languages and type systems, to see how the framework can be extended. In theory, a lot (such as the entirety of SML) could be instantiated currently, but it would be quite cumbersome (here's what the implementation of the currently instantiated language looks like https://github.com/jeprinz/pantograph/blob/main/src/Language...). So we're working on trimming down the formalism and developing new abstractions to make things easier, and to support some more advanced typing systems that actually would have problems with the current system.