You knew before buying it that it would only be open to guild members to enter willingly or to people you choose to invite, if you don't think it is worth $5 you shouldn't of purchased it.

I like the idea of Guild Halls for guild achievements like guilds reaching x number of GS wins, PKs/BKs, etc, but the way Graal is adding an update like this for each individual guild is not something that would really be much of a priority IMO. I think if anything like this were to be added, it would just be one single building on the overworld in which it records and displays all guild achievements, who knows, maybe it could be a good spot for guild recruitment. Pretty much just one big central all-purpose guild themed building.