Change the recalibration model so we don't have to keep all the trash just for the single attribute to put on a decent piece. Without that trash in the stash we'd have a tonne of free space. It is high time you realize how bad the current recalibration system is for the game and that's besides wasting a tonne of space. It has all the wrong incentives for players because it promotes a conservative approach to build improvements.
Say you find a nice 10% weapon damage roll on the backpack. Do you put it on a current backpack that's decent but due to insane RNG on the backpacks still quite a distance from ideal backpack? Since nice weapon damage rolls are rare what are you going to put on a better backpack when you might find it if you use it on a current one? The same roll from the current backpack? That destroys the current backpack that wasn't ideal but still nice and which fitted a different build than the better backpack you just found. So to avoid having to destroy a nice backpack or be out of a roll for the nicer one when it eventually drops, you stash your best roll and wait for a suitable recipient.
Or say your pretty much perfect favorite mask has 45% DTE and then you find a 50% DTE roll. If you put it on, you just wasted an inferior but still nice 45% DTE roll. You are also relatively likely to find a roll over 50% DTE sometimes in the near future so if you slap 50% on now, are you then stuck with this roll on your best mask, or do you waste 50% as well to change it to 54% when you find that one? So you again wait in order to not make a hasty recalibration you might come to regret.
One more example to hopefully get through to you. Now you have a very nice vest and you'd like to decide whether to roll headshot damage on it or chc. If you put a low roll of either to test you won't get usable feedback because the low roll won't have enough of an impact. But if you put a high roll on, well then you're either stuck with that one and can't try the other, or you're going to destroy it just to try the other which might then even turn out to be the subpar choice in your specific case. And yes the specific case is relevant because on a different vest, with different talents and different other rolls a different choice might work better. So again instead of promoting experimentation and playing around with your builds (which I assume is something you'd want to promote) your system acts as a break because the material to work with is rare, its acquisition supremely unreliable due to RNG and all the changes are destructive.
I know many players with these and other considerations that cause them to play it safe, to use a wait and see approach and thus stash many of their best rolls which then aren't doing them any good. All because of the flawed recalibration system you came up with that is in no way an improvement over the one you have in TD1.