My idea is Dna market. There are two parts to this.
One of the parts is the easier one, player-bank. You can trade unwanted dna for cash, coins, or even other dna. You can select a creature, select the amount of dna you don’t need, and the resource you want. Each resource would have a different rate for different rarities. This only works for common, rare, and epic.
Cash: 10 HC/200 dna
Coins: 1000 coins/200 dna
Cash: 20 HC/100 dna
Coins: 2000 coins/ 100 dna
Cash: 50 HC/100 dna
Coins: 5000 coins/100 dna
Dna trading would be based on hybrid fusing prices. For example: common to rare: 200 to 50. Common to epic: 1000 to 50
The second type would be player-player. This would involve an entirely new section on the bottom of the screen. You can put dna up for sale publicly or in your alliance. Only once a day(to avoid overcrowding and spamming). Anyone can come in and buy the dna, and has an option to tip the seller. The seller can choose coins, cash, or other dna as the price. Selling rates are 2x as much as player-bank.