I've always been in favor of having one or two weapons that were allowed to come with you throughout your journey. A weapon that stays relevant by being able to be upgraded to keep up with the scaling of future content. Let's say...a piece of material akin to Etheric Light that turns your Legendary weapon or armor into "Legacy" weapon or armor. But limit it to one piece of material per character or something. However, I think it's Bungie's responsibility to make it worth my while to use and cherish new weaponry. Give me a legit reason to drop the old gear and use the new stuff. Make the new weaponry fun to use. Make it aesthetically pleasing. Make weapons that are truly unique. Yes, it sucks knowing that the hours I've spent grinding to get and level up weapons is kinda gone to waste with each new expansion. However, if the weapons and armor are awesome, fun to use, and cool to look at? Makes that bitter pill a little easier to swallow.