If they want to create caves for the anti-socials so be it. Guild Halls would be neat as a new form of instanced housing, like a place to gather before a raid and such. Perhaps allowing all guild members access to the Guild Bank (only) as well as place one sales crate per member.
Beyond that.. I think anything else is just over kill. It rings similar of the chat amongst crafters who want to hole themselves in their homes instead of going to the instances. Frighteningly similar requests from that group as well. "I want a bank, and a wholesaler and one of each node should spawn on the floor of my home so I can harvest at home too, and, and, ummm.. A Snack Bar!! Yah!" :P
Regardless of what they come up with.. I hope the halls are instanced like housing. Freestanding structures clutter up the scenery as well as make paths between different areas, variable obstacle courses. Free standing, customized housing was a disaster for UO for example. Not only did it take twice as long to run anywhere because you had to navigate the "neighborhoods" of houses. But, they were unable to merge servers going forward no matter how small the populations because houses would overlap and real estate was going for as much as $5000 in RL money.
Finally, on the PvP servers, free standing structures become little safe zones where people can fight like snipers. Chasing or running from somebody is a nightmare and nothing more than a test of mouse agility. :P
Guild halls will be "neat" but I hope they don't have all the bells and whistles that many of our more "imaginative" players have been asking for. And I definitely hope they aren't free standing.