Things like this have been tried many times before. (I made one myself back in the day). It always seems like a great idea up front, but never ends up quite working out.

One of the big things is that the benefit declines over time. The amount of code reuse you get is sub-linear with respect to the size of the project. As the project matures, GUI code and back end code diverges. That leaves you stuck in a framework that ends up not necessarily optimal for server side, and not necessarily optimal for client side, and the amount of code you end up writing to coordinate between them ends up outweighing the actual business logic.

The things that are successful tend to focus on problems that increase with greater than linear complexity as your app matures. Spend time focusing on these instead. Don't lock yourself into a framework that prohibits it.