We all know scarlet wasn’t inherently evil. She was rumored to come from a different tree far away and became evil due to a mislapse in the experiments. So, I had this idea
In the new zone Magus Falls en Maguuma Wastes. 2 zones above and 2 zones below the border of the two areas. As well as a fifth zone overlapping that border. There are two trees; Yu’Auraa, (as the grawl named it) and the Old Red One. These two trees have different teachings and ways of life that collide. The trees have their own areas, but the overlapping zone is a combattant one. A guild can allign themselves with one tree they believe is right, and then fight for their cause.
(yes, this would mean the sylvari here do not follow the teaching of ‘all life is sacred’)
In this bordered zone there will be a line seperating them. Along the line events will ocure. Completing the events from one side before the enemy can complete theirs will the push the border in your favor. The more you control, the more benefits your alligned guild will get. (favor of the tree)
There can also be an instanced battlefield in the centre, of an old grawl temple where the two trees would love to connect to. Here 15 players of one tree and 15 of the other battle. One side must stop the Oakheart from getting to the plaza in the ruins, the other side must protect the Oakheart to said location. The defending group is the one whose tree is currently dominant in the ruins.
This idea is based Kurzick and Luxon, but this time tyrian in background
As for the dragon part, in the two seperated areas the trees fight against the dragon. In the middle zone they fight each other. And you as the player must help the two trees to at least agree on helping each other in zones even more west where they have to work together fighting the dragons.