JetSpeed RSS infrastructure:

Store all RSS subscriptions via PersistentDocument into a flat relational 
database.  This way I should be able to do a DOM query with SQL performance.
This would allow people to do an XML database search.

Custom RSS support.  Ability to create, publish and set ACLs on a your own
custom developed RSS channel.  Possibly even the ability to subscribe through 
all custom channels  (an "add to my RSS channel" button)

Integration with XMLTree.  RSS subscriptions should be done through Cocoon 
styling of XMLTree RSS subscription portal.  With backend integration into 
JetSpeed's core servlet.  Also this should be an open public publishing mechanism
(assuming the user agrees that they won't keep the URL private which might have
to go into another license TODO.  I am not sure teh APL applies to publishing of 
content.)  All publishing URL's CGI' should be done through a custom XML dtd 
(or a standard one if one exists) which specify the HTTP method, URL, etc.