It is normal for an user to call the Format > Character dialog and make changes 
to the font, its size, other specifics etc.  

Now for applying the changes we can provide a wider spectrum of options as 
follows.  

It would be a combo list at the bottom of the dialog.  With your concept of 
trees and other changes to be incorporated to Q this would be more easier.

Apply changes for -->Selection
		     Paragraph
   	             Whole Document
	             This section
	             Update Style

This option would help the user to make wide reaching changes in the document 
which would other wise take him long steps.  

Please give a thought.