Guild halls should have message posting boards so information can be shared. Also, there should be a poll function, where members can vote on things, like new guild halls.
There should be guild "banks," an accOunt guild members can place, but not withdraw, platinum. Only the guild master would have control, and the platinum would have to be spent on guild-wide items (eg a guild hall).
There should also be more things to buy for guilds. For example, a guild may require members to wear a certain piece of vanity armor. The guild should be able to get these items at a discounted price and with varying sizes of orders and discounts (eg 10 antennae saving 5 credits and 100 antennae saving 75 credits [not necessarily such large discounts, just an example]). On the same idea, guilds should be able to design a logo which would appear on their armor somewhere or a color scheme.