Nit: Perhaps you meant to say “with a language server”? There’s only one Language Server Protocol, but multiple language servers and language clients.
While filling this out, I realized that it’s really hard to answer the question about what typing needs the most in terms of new features. I didn’t realize this while looking over the proposed questions, but filling it in, I found I was choosing pretty much at random from a bunch of orthogonal missing capabilities.
With the benefit of hindsight, I wish I had been asked to rank several well known ideas, and separately for a key feature not listed. Of course, I say that imagining that the list would contain exactly the features I consider important, so take this meta-feedback with a grain of salt.