Love the ideas so far. a few things....
if an GM/Officer ginvites a toon the addon should check the blacklist. should said toon exist on the list, a popup displaying ban/blacklist info on that toon should popup. this will help lazy officers from inviting w/o looking up the blacklist.
also, by recruitment rules, do you mean a checklist of lvl/class/pertinent info, that on a /ginvite would be auto-checked and (dis)allow the invite? if so, bravo.
a nice addition would be a guild help line. this would be kinda like the gm ticket system. Guildies could open a technical (aka: mod/game/vent/compy help)ticket which could go to those capable rendering good advice, and quest/instance help ticket going to.
you could consider about a GM/Officer dnd auto reply msg system so one could let guildies know whats up and who to talk to without disturbing you if you were say raiding and what not.
i know you have a heap of work left before a finished product and i can't wait to try this out.