Essentially, I would like to be able to design a Page. And then, drag & drop that Page onto the canvas, in exactly the same way we currently drop widgets. The dropped page would be uneditable... but these dropped pages should automatically update when the actual Page is updated.

Concrete example:
1) Create a page called "Login" add user/pass fields.
2) Drag the Login page from the "pages" box onto the "Home" page and position accordingly.
3) As needed, edit the Login page and preview results back on the "Home" page.

If there is a way to donate, I will personally help fund this effort.

I don't really need Master Pages, per se. But creating re-usable template widgets would be awesomely useful. I would like the software to easily support the work-flow for http://www.slideshare.net/Titine/user-interface-design-in-practice (starting on slide 21). If that worked, I could get my whole company would move to this mockingbird.