Actualy this can be fixed by the guilds with what they have now.Forums might only allow restricted acces until they know you can be trusted.And for chat information it can be solved by simply be solved with a few group invites.
Basicaly we dont need a new system for that which can be solved with the current one.
Basically it's a crude, but effective method to "put multiple -CLASSIFIED- tags" on certain information by ICly using some kind of protection, be it primitive cyphers, locks, magic among other ways to restrict access to "sensitive" information on a certain guild and OOCly configuring usergroups, both hidden and visible, that have access to restricted areas on foums. And it's entirely possible as well to create multiple "degrees" of clearance using this method, having a gradual increase in access to information to a member according to the time he stays inside a "guild", what is another way to encourage people to remain on it. Equally, "guilds" can have public lists of their members, and of former members on their own forums and IC on their "guildhouses" for others to consult, if they wish. Now forcing every guild to show every name of every single member that is there or have been there, without any chance of bypassing it, isn't something I would fancy.