Add suggestion in the simple search input.
add support for markdown support, add custom PDF export
Leverage existing Rating system provided by LM team
Play with comet, Bayeux ... ( see CommetD and Atmosphere ) or integrate Cloud9, EtherPad or EtherPad Light (Etherpad light looks actually really cool and easy to get started with), or ShareJS (https://github.com/josephg/ShareJS)
Build iOS Automation Client + Simple iOS Application (NB: see http://hg.nuxeo.org/mobile/iphone/ for existing iOS app based on CMIS).
Leverage requirements and experience of PCSOL integrators so as to provide a flexible WCM plugin. PCSOL is coming for this subject!
Test and integrate tools to be able to use TDD and build a real CI when using Android SDK