We do quite a lot of this using webviews in vscode over at Darwinium. Similar process that involves postMessages between the UI container and the host containing the LSP. Biggest challenge I had with this was figuring out how to map a diagnostic from the language server (which is inherently range-based) to a UI component that would display it - it involves a fairly intricate pubsub system and mapping UI components explicitly to parts of a tree. Would love to share it eventually.