Guild Shared Bank:
Have a guild shared bank(that opens up at any banker) where you can set permissions of guild members to put things in and take things out. It would be nice to also assign certain items inside the chest to members so they can pick them up anytime.


Guild Battle Plane:
Have a teleporter on ship (how about planescaller brings you there) transport members to a guild battle "plane". (It would be cool to actually design it a little as well)

any other ideas?