So I have been thinking about this for a while. how about making some kind of content which focus on playing inside the other faction home city?(horde going alliance and vice versa) im not very familiar with the lore, but what would you say about like, having a (for example being horde, Scenario, where the goal is to d some kind of damage to Stormwind in some kind of way?, or maby Exodar, to bring some ppl into a dead city with a (maby) reward, as for alliance=Sm City)Horde have the Theramores fall Scenario, so I don't see this impossible. Thinking about this example with the Hozen quest chain in my mind(like lvl 85-86, Jade forest), it end up catching Adrian Vrynns son. Since in Cataclysm a dragon(which were easy in LFR ) And this giant fellow made an great damage to the whole world of Azeroth, so why wouldn't the players be able to do some harm to the opposit faction aswell?
Players already can enter a faction city and attack it. They just have to prepare to have their faces stomped into the dirt and bring lots and lots of people unless they are on some server where one faction outnumbers the other 5+:1
You can even get awards and achieves for downing the racial leader.