I think it would be cool if Hive tried to invade and everyone inside the tower gets there point of view changed to 1st Person and has too defend the tower. They can have this as a random event, would be fun to have at the tower. Bungie can even announce when it is going to happen, and that it is a one time event.
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I like the idea but the tower seemed to be and so focused on being a peaceful and chill place where we can socialize and rearm before going out to the wild again. I think maybe Bungie should plan on making an actual city area and release that to players so that stuff like what you mentioned in your post can happen, maybe. The city can be bigger than the tower, and aim to be a social aspect added to the game. But also big enough to have an invasion from fallen or what not happen. That'll be cool.