These seem clearly not designed to stack and it'd be unreasonable to let them all, but if you were going to allow any of them to stack, which and why and how many stacks?
Order of the Dragon:
Aid Allies (Ex)
At 2nd level, whenever an order of the dragon cavalier uses the aid another action to assist one of his allies, the ally receives a +3 bonus to his armor class, attack roll, saving throw, or skill check. At 8th level, and every six levels thereafter, this bonus increases by an additional +1.
Helpful (Halfling)
You see nothing wrong with letting others achieve greatness so long as the job gets done.
Benefit: Whenever you successfully perform an aid another action, you grant your ally a +4 bonus instead of the normal +2.
Creed of Protection (Virtue)
Prerequisite(s): Good-aligned. In addition, you must always stand up for those weaker than yourself and defend your community against those that prey upon it.
Benefit: When you use the aid another action to improve an ally's AC against attacks, the bonus increases to +4 instead of +2.
Especially combined with:
Bodyguard (Combat)
Your swift strikes ward off enemies attacking nearby allies.
Prerequisite: Combat reflexes.
Benefit: When an adjacent ally is attacked, you may use an attack of opportunity to attempt the aid another action to improve your ally’s AC. You may not use the aid another action to improve your ally’s attack roll with this attack.
Normal: Aid another is a standard action.
Thoughts?
