There needs to be a better system for allied guilds. Many guild have spun off sister guilds or are working together with with other guilds. Can a system be developed to identify allied guilds, one that allows for sharing resources and or rallies. The level of cooperation can be set by the guild leadership.
Good idea, but if you can do everything with your allies that you can your guild, then why not just increase how many members can be in your guild? Perhaps let allies show up as a different more friendly color than orange and allow allies to reinforce each other, and maybe implement an Enemy system where marked guilds show in Red colors.