as it is, there are set stats you can get, up to a certain +. if you get one ring, and want different stats on another, but get a dupe on the first your second run. its useless. So to be able to turn it in for a certain combo of stats of your choosing.
TBH i don't use sewer items, but it would be helpful to get stats you actually need, like ruby, instead of a rng on three different items.
imagine doing ruby favors, and the item being a RNG of her given stats.