> But there's much more to that comprehensive goal than just writing a renderer in Rust.

Which is why the latest Servo builds have very strict sandboxing. People assume that Servo's security story is "just write it in Rust and it'll magically be secure". In reality, nobody on the team is that naive. The goal is to create a browser engine that achieves and significantly exceeds the state of the art. The architecture for that exists right now.