"document commit" possible?

[Brian Whitman]

Could the commit operation be adapted to just have the searchers aware  
of new stored content in a particular document?
e.g. <commit id="abc123"/>

With the understanding that queries for newly indexed fields in this  
document will not return this newly added document, but a query for  
the document by its id will return any new stored fields. When the  
"real" commit (read: the commit that takes 10 minutes to complete)  
returns the newly indexed fields will be query-able.