No, you can't target specific symbols. You can however convert item to "Optimized Graphic" within Catalyst. This will speed up your application perfomance because there will be less code.
Catalyst does not have the ability to pick individual symbols out of a SWF. You'll have to export each symbol as a separate SWF or do this part in Flash Builder.
Great feature idea, though!
It's indeed a nice feature! And somewhat nescessary.
It was my first question at the Adobe User Group meeting in Amsterdam last june 3rd. How about asset management and replacing your content. The current round-tripping is not that spectacular. For Catalyst to be really succesfull some fine asset management is needed cause the process of development and design will go parallel instead of linear.
I think Catalyst should take a look at Indesign his asset management. That works great, also the example as Flash with symbols is a very good idea. Furthermore maybe a look at Encore is also an idea. They fake symbols and recognize layername's and convert them to buttons like this: (+) for a button and (=) for the highlight of a button.