Since Bungie said that Taken can appear any where I think that Destiny needs a game mode where the Taken attempt to wage war on the Guardians in the middle of a mass scale Crucible battle. Basically, PvP with extra large maps, Taken, maybe a few bosses, objectives and, 10-14 vs. 10-14.
Warzone from Halo 5 put into Destiny is another way to describe everything I wrote.