What does "a better sense of agency" mean to you? What I am reading of this suggestion is it amounts to a dislike of roll chances and wanting there to be an alternative around that roll chance because it is "frustrating." This amounts to the same suggestion as
increasing the loot rolls, but the substance of the change suggested, in either case, seems to just be that everything should be easier to get.
How is the collections economy unstable? And how would this change make it more stable?
If implemented the way its rolling around in my head, it would not be "easier" it would just be a feeling that you could see progress. Not only waiting for some random chance that could happen on the next item, or it could be 30 more hours of grinding.
If you as devs want this item whatever it may be to drop approximately every 1000 "events", and some other item to drop say every 100 "events". If after 1500 I do not have the first one, but I do have 15 of the second one, have I not done enough work to have "earned" the rare item. Then I could trade my effort, not my luck, for the thing. It's just a thought. RNG is incredibly frustrating, but I don't want to make it easier just more reliable. I'd see trading the equivalent of 1.5 times the expected effort of the actual item. Maybe you get lucky and get it sooner anyway. Maybe the odds come out exactly as intended and on your 1000th (in above example) you get it. But if RNG is not in your favour, and you run way past the intended grind, you can buy out with the spoils of the effort you put in.
Rare item drops don't sit around on the market, they are snapped up right away because rare is, rare. This means a value can't be established for them. Any given transaction is more about the luck of who happens to see it first. What sells for 200k this week, might sell for 1M next week, and 150k the week after. Being able to construct the value of all the items in a set around a building blocks of lower level items would allow prices to normalise.