Resetting the whole weapon doesn't make any sense. Why not just 'reset' the last three damage nodes and leave exotic leveling as-it-is. That-way exotics still keep their perks (remaining viable for content while leveling), the damage for each weapon upon resetting stays at 300, but the damage nodes raise it to DLC appropriate levels. Think about this in the context of the game. Why would we have to re-unlock what are essentially 'learned skills' with a particular weapon? What 'needs to change' about the weapon for the new content isnt how the weapon performs, but rather how much damage it's doing. Just make us re-level an exotics damage rating, not its perks.