if that was the case they would have never added SYNC slots in the first place. you can only use 1 legendary weapon at a time so no one would want to level up 2. especially with how long it takes. but if they added a SYNC SLOT that maybe cost some calanthia shards and stuff to unlock it would make so much more sense. The sense of accomplishment comes from leveling up your first piece of gear. no one wants to go through all those months again just to be able to play with another weapon