I don't know if "from scratch" is really a fair statement. React accepts HTML in the render function, so the only thing you'd need to do is modify the variables to match JSX's variable syntax, which is exactly what you'd have to do with Vue.
I think it's all pretty much the same deal. You might argue Vue's template syntax is closer to HTML than JSX is, but that doesn't really feel like the major issue when slowly refactoring a large application.
I think it's all pretty much the same deal. You might argue Vue's template syntax is closer to HTML than JSX is, but that doesn't really feel like the major issue when slowly refactoring a large application.