I'm not sure if you want to add new Features to the guild.
What is missing:
Alliance and Guild Calendar!
If a guild sets a Date in Calendar for an event all Alliance members could read it and participate if they want to.
Because of different timezones atm many people missing whats going on.
So Calendar would solve this! You can say to everyone check Calendar for upcoming guild or Allliance Events!
It should not be very hard to implement