I have decided that acording to the will of might Sithis and the Night Mother I shall personaly strive to remove all Thalmor scum and their activity from Skyrim...but would this break the main quest or should I just finish up the Civil War and Main quest before this most holy of crusades?

Get past infiltrating the Thalor Embassy, rescue Thorald, commit Thalmor depopulation for Sithis.
Too bad the Thalmor are set to respawn. Once your character has reached a certain point in the Game, Elewen is not an essential character