This looks really cool. I’ve wished for something like this to exist for python for a long, long time. At the same time, though, a lot of architectural benefits come from elevating front-end code from being an afterthought of the backend application to being a first-class citizen, an application on its own. In a nutshell, separating the two and having them talk over an API allows the developers to code using the strengths of the front and backend environments instead of making concessions to find the common ground.
This approach, provided it matures enough, will probably lend itself very nicely to rapid-prototyping so long the migration from the prototype to the more mature code can be painless and gradual (e.g. the way you can slowly strip out django component by component until you are no longer using django).