Each guild could set "laws" and "quests" that can affect a member or friendly's standing with the guild, and would provide a more active diplomacy system. This would also serve as a quasi-legal system to know when your guild members and neighbours were complying or contravening your "laws".
E.g. a neutral player invades your land and destroys some property when nobody is looking. Their alignment with the guild is reduced by an amount set by the guild person per in charge of alignment who is notified of the name of the player who contravened the "law" and what their corresponding alignment penalty is.
E.g. a friendly player wants to support their neighbour's effort to construct some buildings, and accepts a posted quest to supply x building logs. On supply of the logs, an alignment increase with the receiving guild is awarded to the player and a similar notification to that above is sent to both the helping player and the guild person responsible for the alignment system (say a viscount, for example).
E.g. a guild knight defeats multiple enemies of the guild in an instanced battle, and receives a corresponding guild alignment for his/her battle prowess.