Oh didn't know the sellable items were removed from the defeated pokemons drops.
But I think being able to sell items like potions and evo stones for a % of the their buyable price would be nice as all your pokemon dying has very minimal consequences since you just get sent back by 1 floor so there's not much incentive to be healing your pokemon, I usually find my self having around 100+ of every item by the time I prestige so being able to sell them to get a little extra money to gamble with would be nice.