I want a web where we just draw on a big canvas. That's a pretty simple API for implementers to get right. Then we could move the scene graph (DOM) and it's rendering engine entirely into the application language where it could be more readily hot-fixed. It'd be like PDFJS but for your whole fucking web browser.
Have you looked into the Famo.us project? It's not my cup of tea in terms of implementation, but it sounds like exactly what you're looking for. Alternatively, what's keeping you from just using <canvas>?