Since the outfits never change, just remove them & replace with a special voucher to buy only the arena award outfits. People who get the top ranks (bronze, silver, or gold) get enough to buy in their rank’s outfit in the outfit shop immediately, but also so you can save up & buy higher tiers too eventually (gold obviously being the highest & taking the longest to save for if you don’t rank first). Because there are only so many leagues to go through the arena & you can easily get stuck in one for a very long time. And especially at the lower leagues it’s easy to not even rank bronze and yet still get promoted so you skip a bunch of chances to even get the prizes.
I have been ranking at least bronze for months now & by this point should have the entire rotation of bronze outfits for every hero, but it’s only ever been the warlock the whole time.
Also there’s a display error with the bronze warlock set that shows one piece of silver (but still shows up bronze on the hero). The silver set has the bronze piece.