I understand there are limiations to the game, preventing certain things but is the game limited to a global shout? or at least a shout that can be seen in areas that SE wants more populated? (Port Windy/Sandy/Jeuno/Bastok Mines/White Gate)
If a Global shout, or linked shout between the cities is not possible then people will never leave Jeuno because of the convenience of getting a group of people together for a party, not many people use their LFP flags now these days, I'm sure you notice that.
Doing a search now results in 19 people in all known areas using the flag, of that 7 of them are between levels 75 - 90.
If SE is worried about the congestion of Port Jeuno, why not look to adding the NPCs to Whitegate? Whitegate is a much more flexible zone then any other location in the game, able to teleport from Whitegate to Jeuno or your home nation at any time, and have access to it from all the major cities in the game.
I know that when Abyssea was released it was based around Rise of the Zilart, and Wings of the Goddess, is the community that worried if they add a extention to all three Abyssea titles that it will prevent all the current owners of Abyssea, Zilart, and Wings of the Goddess from enjoying their content?
What would the possibility then be of adding a quest for those who have Treasures of Aht Urghan, to expand the reaches of the Abyssea NPCs and place them in Whitegate and Nashmau, would it be that memory expensive to implement into the game, as you've already stated some zones are at or near cap memory that they can hold for those playing on PS2 versions.