Even ignoring the rest of the post, the idea of a Green Slytherin based off of Avada Kedavra is interesting for many reasons.

Let's look at some of the implications:

• Avada Kedavra and the Patronus Charm (2.0) are basically mutually exclusive. In order to cast the first, you must want someone dead for the sake of being dead, and in order to cast the latter you must value all life to the point of denying death altogether.

• Avada Kedavra and the Patronus Charm (2.0) cancel each other out. We saw this in Azkaban, and at the time we probably assumed it was just a result of Quirrell and Harry's magic going out of control, but on closer inspection it seems that both simply destroy the other, matter and antimatter style, which makes sense considering what type of magic they are created from. A magically created preference for death over life, and a magically created preference for life over death.

• They both also follow the political lines, as you mention above. Avada Kedavra is more likely to be known and cast by those desperate for someone to hate, and the True Patronus is more likely to be cast by those who are trying to cooperate, simply because those mindsets are more likely to lead to those specific preferences.

• Now that I think about it, the two groups are also the 'Cooperators' and the 'Defectors' in the Prisoner's Dilemma.

• The interesting question is if they are going to devolve into standard Green vs Blue political idiocy. If Harry has a controlling power, they may not, but I don't think Draco has progressed enough as a rationalist to be able to avoid all those old lessons yet.

There is probably more here, but I need to sit down and think for five minutes, and do a quick read through of the archives.