As a user I prefer everything on one page, as it saves the toing and froing between MainWindow and Dialog box. Plus I think most users are familar with the left search bar, right content pane approach from websites and also Mircosoft applications like,
Word etc
I think you can still create a framework that is easily extensible. If you create different panels for the logical sections and use a flexible layout manager without absolute positioning, you could easily add new panels at a later date.
His motto is "User First, Implementation Second".
Whilst I may agree with the sentiment in the real world, for this assignment the most important thing is to implement the requirements!
Jason.