i like the way you think your ideas are different than I have heard before. speaking from a lore perspective your gear is obsolete compared to weapon foundry gear and would never compare (exotics being the exception as they were fashioned to be closer to golden age weaponry). making your old weapons obsolete would improve your experience because it would be like playing the game for the first time again. as your experiencing the story you also get the thrill of getting better and better guns until finding your new max weapon. being able to run the taken king all the way through with out picking up a new gun could ruin the taken king for you. I suppose other players would not be harmed by legendary weapons being able to be carried over its more so to force you to explore the taken king to its fullest