you sure could. But you always are faced with surprising behaviour when you open a part and "nothing happens". I'd prefer the IDE to handle that for me whenever it is obvious that my screen resolution and/or hardware setup (number of monitors) is insufficient.
I also must admit that I don't have alt+space in my mental toolbox
Taking a little detour:
Most of this stuff would go away in an environment like Eclipse. If everything was a frame within a perspective, the perspective would be the context for display. There'd be no sense in saving a window size if everything just took the space that it was assigned by an inidividual context. I am not saying I want Eclipse for Smalltalk, but I think most Smalltalks should adapt some of the GUI behaviour of eclipse. There is, for example, not necessarily a need for every single Browser to bring its own navigation component (Hierarchy, Application, Senders/Implementers), a central, context-aware navigation pane that switches its context every time an editor is selected, would be a much better thing, especially if it provided options like a history and back/forward buttons. This could both save real estate and improve developer productivity.
Instantiations has (had) the perfect set of knowlegde to work in this field, since they've built some top of the breed Eclipse plugins...