This doesn't really make sense the browser is complex because it needs to do a lot in order to meet web standards. Removing most of it's functionality and making it a VM with a cross-platform renderer is definitely a great idea for building cross-platform applications but it's no longer functionally a browser. You could build a browser engine on top but then that's just circuitous and most likely slower. The standards and complexity don't vanish in either case. Neither does the VM and renderer obviate the need to follow the version and configuration of that piece of software. And importantly you don't need to use the DOM right now if you don't want to in the browser as Figma and other applications clearly demonstrate.
If what you're trying to say is an application platform based on WASM and WebGPU that safely sandboxed userland applications ultimately delivered over the internet is a good idea then yes I'd agree it is. But it's not a browser.