Any suggestions on any of the issues mentioned above?
Most of features you have asked are present using GateIn and its extensions specially eXo content (WCM and DMS). You just need to be more throrough on your research and do some work integrating them.
You have mentioned "Portlet to Portlet communication (each portlet with different .war file)" but this is a feature of any JSR-286 compliant portal servers such as GateIn or JBoss Portal or others. As I said, you just need to be patient in your research. ;-)
thanks for your reply, unfortunately i still couldn't find the stand alone extensions that can be integrated with GateIn.
For the second part, Portlet to Portlet communication, I had tried once before with no luck, but tried it again with a fresh project, it works.