I posted on this earlier, but make the raid much richer in loot drops (Y1) and increase the trade-in of shards and energies for glimmer to 500 per either type of raid drop. More loot is useless for year 2 but it becomes a great source of armor materials, weapon parts, and glimmer. I would run the Vault of Glass every week if I knew I could reload on armor materials, weapon parts, and glimmer easily. If you don't need more there are always faction packages to earn by using these items to rank up. This would maintain the year 2 weapon balance while creating a new purpose for the old raids that would actually be useful for year 2 players.