I wrote this post a while ago, but it disappeared so I'll post it here.
Make guilds be purchased from an NPC (Maybe from someone in /join tower?)
The person that buys the guild is the guild founder
The founder can create and name his own ranks for the guild
Make a system for guilds that allows members of the guild to level up by getting, say, honor.
Allow the founder and anyone he assigns to make quests for the guild that give only honor.
Make a system that allows the GM's to give members "guild badges" which would be personalized badges for doing things for the guild. These badges would not go with the book of lore badges
Assigned guild members can recruit, or people can apply to the guild.
Guilds should be able to level up by guild members doing things. For example: Leveling up themselves, donating gold and ac's, or recruiting people.
Guilds should have a bank where players donate gold and ac's to spend on things
Variety of styles to choose from that level up with the guild. For example, you could choose a swordhaven or shadowfall theme and they would look different, but they would level up the same by starting with just a guild hall, then a small town, then a full castle.
Have a message board where leaders can post announcements. Should also include a guild roster, and the quest board.
Use money in the guild bank to buy guards, buildings, stores, and other upgrades for the guild town.
Guild members cane set the center of town as their spawn point for when they log in
Enemy guilds can attack the town and get some kind of bonus for destroying it. Like the guild town is inaccessible due to repairs for a few days and the enemy guild gets a wealth of the gold transferred to their bank.
Guild Leader should be able to set the guards skills and/or tactics for when they are attacked. For example the leader could set the guard to attack healers first or use a certain skill in a certain condition
Enemies should also be able to buy siege weapons for when they attack another's town.
The general layout for a max-level town would be something like this: you would start at the front gate where some guards would be. Then you enter and there is the town square with a few buildings. There is a screen to the right and left that have additional buildings and shops. Going up from the town square there would be a gate with a moat in front of it and a super-strong guard. Inside the castle would be custom NPC's that could be set to look like the guild masters. When all the custom NPC's are defeated (there would be one in every room of the castle), then you would win an attack. Siege weapons would allow you to do things like instantly destroy the gates, thusly skipping a fight.
Enemy guilds should automatically be placed on opposite teams
Allies and fellow guild members should be automatically placed on the same team
Guild leaders should be able to set up private rooms for guild wars where they can set the rules for the match, like no potions, and have the fight be officially recorded or not. Both participating guild leaders should have to agree on the conditions.
A match recording functionality would be cool, so you have proof if the enemy cheated, or that you won, or you can look back and see where you messed up.