Extended XForms can be improved in a number of ways:
Somehow rewrite the layer connecting JavaScript and XForms entirely in XForms code. If doable, Extended XForms will no longer depend on a specific implementation, opening it up to be used by a larger group of developers.
Improve the transformation to account for what needs to be included (CSS and JavaScript code) to reduce the the extra footprint. Also bundle the code in one file, rather than loading multiple files.
Streamline the way we write components, allowing for easy updates, easily removing unneeded components, and adding new components. Also, allow the users to write their own components to use in their projects or share with others. This will bring faster updates and help the project not fall behind the rapid growth we are trying to match.
As for the performance issue, there's only so much we can do. The only way to work around that is to write a new XForms preprocessor/renderer from scratch, which is not a somple task by any means.… but doable... maybe?