I like the idea of seeing a whitelist added to guildhalls, so that if the guild would rather keep the hall private, they can still allow a few select individuals in. Or alternatively if a guild member of high enough rank (officer or above) was able to directly invite a non-guild member into the hall.
Perhaps also a blacklist for public guildhalls, if they've been struggling with troublemakers.
Sorry if this has already been suggested, just my wee idea.
Sounds interesting. No whitelist, but the guildhall invitation idea is good.
Also, blacklist/guildhall-ban helps a lot. It was, after all, on the original guildhall thread.