These are the only "Advanced Super Ninja Search Options" I am aware of:

*(hit <return> on a blank search to see this list)*

 - **proposals in a specific category**  
e.g. category:technology apples oranges  
 - **proposals created by a specific user**  
e.g. user:1234 apples oranges  
e.g. user:me apples oranges  
 -     **proposals with a minimum number of followers** 	
e.g. followers:15 apples oranges  
 -     **proposals with a minimum number of committers** 	
e.g. committers:15 apples oranges  
 -     **proposals with a minimum number of views** 	
e.g. views:250 apples oranges  
 -     **proposals with a minimum number of questions** 	
e.g. questions:1 apples oranges  
 -     **proposals that have been closed**  
e.g. closed:1 apples oranges  
 -     **proposals that have *not* been closed**    
closed:0 apples oranges

    The above options can be freely combined in any order

In terms of a [feature-request], there wont likely be many feature like that added to [this-generation system](http://discuss.area51.stackexchange.com/questions/5089/next-generation-of-area-51/5102#5102).