My idea is to put an "invite to guild hall" button beside the invite to guild. Any officer can do this and any officer can revoke or "kick" the person from a guild hall.

When invited, a person would be allowed one time into the guild hall. They could meet the other members. However, as a restriction, they could not access the cheap stim packs or elixirs.

The idea is to allow people in to see what a guild is like before actually joining and to allow friends from other guilds into your hall (hopefully this won't be used for poaching).