Here is a Idea for you :
Create XX lots of maps (like a castle for example).....
Create a set of Keys - key1-whatever
Create a NPC to check for the Key and Teleport acording to the key in Bag.
Create Tickets - again matching the keys
Make a NPC in said Guild Castle that sells Tickets to Key Holder only.
Now create a shop in there that buys and sells everything but make the price really low...
Now im not sure if MIR2 saves the contents of shops when you reboot like mir3 does, if it does not, then scrap this idea as it wont work.. Theory been that the guild sell all there items to this said shop, only the guild leader (or person with key) can Buy the things back.....at low price - like 1% say...
Only thing I can think of right now...