I humbly suggest a few rules for fighters that would/could find a home in this Supplement:
Back to Back Fighting, each fighter gets +1 AC bonus because he need not worry about flanks as much and can focus on his frontal attackers.
Similarly expanding on the Back to Back maneuver,
Shield Wall, Three or more fighters with shields can work together to add some extra protection from the companions. A Fighter gets +1 AC from his adjacent warrior companions by working together in combat. If three fighters work together, the ones on each end get +1 AC, one in center gets +2 AC bonus. Works especially well if five or more fighters can form a ring so that each warrior has both sides covered; each will get the +2 AC bonus.
Defensive Line, The front line Fighters (shielded and usually heavily armored) give additional +2 AC bonus to the archers or other such 2nd row combatants (such as spell casters), because they are actively fighting defensively and deliberately blocking attacks aimed at those behind.
Creating game materials? Monsters, spells, classes, adventures? This is the place!