The "Aura" concept sounds similar to the friendship system in Shining Force 3. It's not that easy to explain, but when two characters work together (say healing each other, attacking the same monster) they gain "friendship points". Once these reach a certain amount, they go up a friendship level. Different characters have different effects, and the higher the friendship level the greater the effect. The highest level also increases the range.
For example, the lead character may have a high friendship with an archer. The archers effect is to increase accuracy, and the leader's is to increase attack. So standing an archer next to the leader is a good move, as both benefit.
It's a cool system, and one I'd like to use.
(I apologise if you already knew all that

)