Here are some suggestions I think we can all agree on.
1) A message board, like a BBS-thing. Reason: Let's say I have an active guild (yes, you may imply I have a inactive guild) and active members. Let's say... member A needs a Iceburst Brandish recipe and doesn't have enough for it yet. He can post it on the board inside the guild halls, where others can go read and accept it. Once member A can pay member B back (or it can be a gift, sharing is caring), member A must delete his message. Located in the guild hall.
2) Last Online date, I enjoy keeping my guild small with active players so I'd enjoy to see when was the last time somebody logged on that way if it wasn't online for 5 weeks, I'll kindly remove it.
3) Possibly a "Apply to guild" option? I thought of joining Team Dai Gurren back in the testing days but I never really worked up the nerve (nor did I know the officers and guild masters) to actually ask for approval. I think it would be nice to have a little "Apply" option.

Thanks for reading.