Be careful about how much power you give a player. If the players abuse the power they are given, then demote them, or remove some of the options from their current rank.
Use Guild ranks as a method for rewarding good guild members. Start members out with very little. Add ranks above the basic starting rank with additional options for players to earn with good behavior or performance. Only your most trusted members should have access to the most powerful options such as officer chat, officer notes, remove player, add player.
If players are abusing the guild chat by spamming or being otherwise annoying create a guild rank that does not have access to type in guild chat. Then demote the offending player to that rank as a warning. You can even do that as a temporary measure. You can promote them back after a period of time or if they agree to be good.
You can create your own names for the guild ranks. Take advantage of that.