I just did a quick search after I thought of something similar, and want to give this idea a bump.
In its most basic form, the idea could just be an NPC add-on to the Guild Hall that sells some of the drink at a slight discount. This could encourage people to hang out in the guild halls... Similarly, there might be a "barkeeper" NPC in the towns, perhaps even a quest to gain a barkeeper NPC in the Command Center in Nightfall...
The barkeeper could sell drinks and perhaps some interesting local food (Drake Kabobs, anyone?) Certainly, since the various upgrade GW has received last year, this concept is now easier to do and I can see that it could lend alot of ambience to the game...
Some other ideas that fits this theme:
--> open air tavern in Kamadan with a barkeep, a minstrel (doing air guitar, flute, whatever) and some random NPCs doing the various dance emotes...
--> a gloomy bar in Bone Palace with dancing skeletons that sings the bone connection song ("leg bone connected to the hip bone") and doing synchronized female necro dance... I bet Joko Palawa would sponsor something like that...
Certainly I think these would add very kewl ambience to the game.