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.
I have read a lot of debate over whether this +3 replaces, or is added onto the +2 provided from Aid Another, on various forums. I am told there is no officially supported ruling from the source material.
Given this, what are the early- and late-game balance implications of allowing them to stack, given feats like Bodyguard that let you provide this bonus as an AOO multiple times per turn, or Ally Shield (which would let you redirect the attack to an ally, and then as an AOO provide them that bonus)?
There are tons of other traits, feats, and features that seem to modify this as well. Far too many for me to list here. So here's a link to a discussion that has several in a build listed for this purpose. Here. Worst case being +26 with a looser GM, and best case being +15 AC. Not all of these are relevant to my question, but some may still apply.