Open Need help creating custom PvP state

[AG]

Heya folks!

Not sure how to title this better so let me try to explain.

Say you have an Alliance and Horde player standing in a Horde territory (Durotar for example). The Alliance player is flagged for PvP while the Horde player is not.
In this case, from the Alliance point of view, the Horde player will have a blue name, meaning he cannot be attacked as he is not flagged for PvP.
From the Horde point of view, the Alliance player will have a yellow name meaning he can be attacked BUT only by direct attacks - until then, AoE attacks, pets, totems etc. will ignore the Alliance player.

I hope this makes sense and rings a bell.

My question is, how can I achieve/mimic this behaviour using an aura (buff)? So that when a player has a certain buff, he cannot be attacked by other players until he attacks first. And to engage combat his initial attack must be a direct attack.

Thanks in advance!

EDIT: Forgot to mention that I use AzerothCore 3.3.5a.
Let me know if I should provide more info

 

[AG]

What I've tried so far is creating custom factions as I thought I could make it work with the "At War" functionality as it is kinda similar behaviour. For example if you are friendly or neutral with a faction such as Booty Bay and toggle "At War" on, you are allowed to attack members of that faction but they cannot/will not attack you before you engage in combat with them, and in similar fashion you must attack with a direct attack first as AoE and so on wont hit them.

Unfortunately, the "At War" functionality does not work the way I hoped - at least I have not made it work yet but I am still toying around with it as I might be missing something.