I like all these ideas.
Re: guild quarters. It might help Haven not get quite so crowded; people can spawn into their guildhalls and then join people on dungeon runs directly.
Re: arcade entrance. I wished the original entrance went to the arcade, not the town square. Unless they're going to add more stuff to the town square, which they haven't.
Re: treasure. This might be a nice representation of shared guild resources. And being able to buy decor would be quite nice. (I miss a sunny, happy guildhall. Maybe we can invest in some natural lighting.)
Re: message board. This idea I love the most, and it would help the larger guilds.