Dear Bungie,
We all noticed that with Destiny2, the legendary and exotic drop probability have been considerably increased.
In my modest opinion, one of the most interesting and triggering activity is to collect all the possibile Legendary sets of armor and weapons, so my suggestion is to improve the quality of the vault, introducing collections for each set (e.g. Cucible, Nessus, Iron Banner, and so on) and, obviously, increasing the total amount of stored items.