What possible use would it be? How big is enough? A thousand slots? 10,000? Even with the vault now you could go months without using the same gun or armor setup twice, so what will making it bigger solve, other than scratching an apparent compulsive hoarding itch? As is, destiny allows more storage space than pretty much every comparable game. Yeah, a few trophy/memory items are nice, but no one needs the old raid armors anymore, no need to keep an old gjallahorn now, and there really is no special point to having every complete set of armor for each class, or every sparrow or ship or shader or emblem stored in the vault (I know someone doing multiple of those, it's sad. They literally don't progress in the game because of an obsession and compulsion over cosmetics). You really want to see everything that badly at all times? Load up one of the database websites with all the images and stats.