This is an excellent question, which makes a lot of sense. We're happy and open to discussing anything that would improve the user experience, and allow others to contribute.
Side note - We're developing the extension for Visual Studio for about 10 years. The functionality has been exposed to the LSP which we only use in VSC. (VS has its own native APIs allowing us very performant integration, and also much more features).
The client-side is not doing much work. Basically, it just drives the LSP. Anyways; there are a few areas, that could be opened:
- PHPUnit integration
- HTML/JS/CSS integration
- extension tests
- LSP API; as you said, this could be used for more features or new things like supreme
- walkthroughs: the API can be used for nice step-by-step tutorials for various frameworks and education purposes
The next step for us is to define the freemium model, and discuss how to make open-sourcing something beneficial for users (we still need to ensure, the extension will work for the majority).
Thanks for bringing this up, we'll be happy to continue with the discussion here.