In the current crafter, under "exchange," you have the option to convert various items into various other items. Mostly this involves converting uniques into other things. Personally, my go-to is to convert 4 uniques into relics to fill out my characters. This is a good idea in theory, but in practice it has two major issues:
It requires identical uniques. You need to collect not just any four uniques, but four of the SAME uniques.
The rewards scale unevenly. If you convert 12 uniques into relics 4 at a time, you'll end up with 150 of them. If you exchange them 3 at a time, you end up with 80 of them. If you convert them 2 at a time you only end up with 48 of them, less than what you'd get for a single 4-pull for three times the cost. This means that it's a huge waste to go for anything less than the maximum numbers.
The main problem this causes me is that it means that I hate having loose hero-only uniques dropping. What this causes is that I tend to stick to a single character far more often than I might like. I have a lot of characters, and I would enjoy being able to switch between them at my whims, just having fun with whoever I want to play with. But in practice, this would cause me to end up with a ton of 1-2 copy hero-uniques, which would junk up my inventory. So instead I end up having LESS fun in the game by sticking with 2-3 "most efficient" heroes so that most of the hero uniques are for the same hero, so that 4-sets build faster and spares don't stick around too long.
For the entire Civil War period, for example, I mostly played Scarlet Witch, and now I'm mostly playing Silver Surfer, because both are highly efficient, but using only one means that most of the uniques I get can be easily flipped. Ideally though, there are a dozen other characters I'd like to throw on for a little while without cluttering mu inventory with junk spare uniques.
This situation also means that it is less desirable to play certain characters with more than minimum unique situations. for example, while most heroes in the game only have five different uniques, maybe six, some have seven or more, to allow for more focused melee or ranged builds, in most cases. This is great for customization, but terrible for unique collecting, because it's much easier to build match-4s out of five possibilities, but a much larger mess to arrange it out of 6-8 possibilities.
So here are my proposed solutions:
Allow these recipes to use ANY uniques, mixed and matched. If it requires five uniques, it can use five Herald's Armors, or it can use a Herald's Armor, a Guardian's Battlesuit, a Mort's Spring Shoes, a Nega-Band, and an Excalibur Tunic. This means that playing any and all characters still gives you useful uniques to convert, not "left-overs" to store up.
Remove the recipe scaling. Make it so that 4 uniques convert to 50 relics, 3 uniques convert to 36 relics, 2 uniques converts to 25 relics. The 3 would be slightly less efficient, but not nearly as inefficient as the current model. This way, you allow players to quickly clear large piles of items, but if they only have a small pile they can still clear that without too much hassle.
Have a serious exchange that only requires one unique. Currently there is nothing to do with one unique. You need two of them for even the bad deal. You can donate them to your pet, but only until you run out of pets with empty unique slots. If you could get a fair trade for single uniques, equivalent to what you could get in a 4-exchange, then you could get rid of spares easier.
But basically, something needs to change so that I don't feel this huge burden every time I want to play as a different character.