Worth Fighting For
flanking house rule
This rule, including much of its wording, is by Skip Williams.
You can disregard attacks from an opponent flanking you. When you do, that opponent doesn’t get the +2 flanking bonus when attacking you and that opponent does not provide a flanking bonus to any of its allies. Ignoring a flanker, however, provokes an attack of opportunity from that flanker, and you lose your Dexterity bonus to Armor Class against that flanker. You do, however, continue to threaten that flanker.
This means that if the flanker is out of attacks of opportunity, you can ignore the flanker (and deny the flanking bonus) with impunity.
If you can’t see (or locate) the flanker, you disregard the flanker by default, and you provoke the attack of opportunity. This meshes with invisibility and concealment rules.
You must make the decision to disregard a flanker as soon as the foe moves into a flanking position. You can change your decision as a free action on your turn. (You still must disregard a flanker you can’t see.)