I am.... ... ... ... a bit confused. We already have a Phase option... granted it is not a "button" but we do. We use LFG. Which granted should be on as default so that people who don't know about it can see and USE IT.
It was a feature displayed in the Flashpoint preview, whereby you could see the population of each phase as well as switch to different phases by pushing that phases button, rather than needing an invite. It was delayed due to a bug they discovered I believe.
Yes, that would be a great and welcomed addition. Would make life easier indeed, There are other games like STO that have had this feature for... forever!