There is no way into that tower, no way to join or otherwise access the champions' headquarters, and no way to disable the anti-dragon shields around the harbour.
I'd guess the headquarters and tower are there for atmosphere. Lar did mention a couple entire regions that cut from the game, but didn't go into any detail if specific quests or small areas got axed. There was a swamp in D2:ED that got cut, and an area containing elves and dwarves (which may have been the same region as the swamp), as well as a Broken Valley type area in FoV. Some of FoV was originally intended to be in D2:ED.
