Guild halls were in Guild Wars 1, why not have them in Guild Wars 2?
An instanced area you can access from the guild management panel, the guild hall you enter could be dependent upon the guild you are currently representing. The hall itself could be obtained as an upgrade through influence, it could even be a high level upgrade for the guild. Access could be limited through the ranking system, echoing the access rights of the guild banks.
Aesthetically the various upgrades a guild has obtained could be shown in the guild hall for example: a guild with lots of gold in their treasure trove could perhaps see a pile of treasure, or as a guilds political level increases emissaries/dignitaries from the various races governments (or orders) could wander about the hall occasionally making a remark. Halls could also be themed off of the architectural influences of each race or perhaps based off of the enemy types. Ex: Having a pirate cave with a treasure trove of gold. Guild’s could even open up their hall to the public for a limited time to host extravagant parties complete with fireworks and etc.
In terms of function the halls could provide; portals to the home cities (or L.A./WvW), unlockable merchants, damage test dummies (like on the Zaishen islands), and a meeting place for guilds that wish to organize before setting off on guild bounties and activities.
On a personal level I feel that guild halls would aid in providing a sense of community and perhaps pride, or accomplishment, to a guild. This in turn would strengthen the playerbase, and make Guildwars 2 an overall more enjoyable experience.
tl;dr I want guildhalls, they would be freaking awesome!!
P.S. Thanks for taking the time to read this sorry about the length and formatting. Please forgive any spelling or grammar mistakes I made.