There's a lot of untapped potential on all of those items, sparrows and ships inclusive. I have always thought that one of the better ways to solve the grand old vault issue is to port vaults to ships, and let different tier ships possess different size vaults. The challenge here is back-end loading (orbit screen resides on one server while individual tower sessions are hosted on another), but it's something that could be considered to be worked around. Shaders for ships, guns, and sparrows would be brilliant to eventually see, though ships and sparrows probably would not ever happen (given that in some cases the colour scheme is all that's different between some of them). Having shells/items/ships reward the player with minimal perks would make them far more desirable for sure!