Now that Guild Halls can be filled with snazzy furnishings there may come a time when one would want to show their Guild Hall to players outside the guild, such as potential recruits, for bragging rights with other Guilds, or to have friends from outside the Guild take a look around just for fun (may also have a bit of fun with 'diplomatic' visits by other Guilds in the future), cause after all how are we to know who has the most decked out HQ if were not allowed to showcase them for prying eyes :P

My suggestion is to allow guild members with the rank of officer or higher to be allowed to give non-guild players a 'visitor pass' that would allow them to enter the Guild Hall for a certain number of visits and/or duration of time. The item would act like a consumable that when used transports the visiting player to the Guild Hall, it could also only be good for a certain amount of time and would expire much like an elevator pass or slot upgrade does.

To prevent people from just spamming invites to everyone they see there would be a fairly costly price associated with it in crowns that the officer or GM giving the pass would have to pay to do so, passes may vary in their duration and cost, e.g:

1 Time Pass - Allows one visit to the GH - 1000 CR (Good for letting potential recruits take a look at the hall)
24 Hour Pass - Allows entry into the GH for 1 day - 3,000 CR (Perhaps for inter-guild visits or matters where someone may need to visit multiple times)

And so on and so forth in increasing time and cost until...

Honorary Member - Permanent visitation rights - ??? (This one may be a bad idea actually)

If a visitor begins to cause trouble and make themselves unwelcome officers and GM's would have the ability to kick them out of the Guild Hall and revoke existing visitation rights, maybe even put them on a 'banned players' list to prevent them from getting future invitations.

Well that's my thoughts on this idea, but what do I know I'm not in a guild myself :P