I had and idea about a way to open doors. What if you had a defined region say a 2x2 section, that when the right combination of 4 wool blocks opened the door. The key could be set by the owner, so say I have a door and to open it you put a green and a pink up top, and a red and yellow on the bottom, then the door would open. Idk if this would be so intriguing in huge smp maps, but it may be nice, if you are wanting to make hidden lairs and trying to go for that Indiana Jones theme. Anywho just a thought.