I don't fully understand the purpose of such action. Mining and minting already run under different algorithms, difficulty and pace. For security reasons incorporating merged mining is also a possibility. Any person who hasn't got a Skrypt or SHA-256 ASIC device could mine Diamonds. If ASICs ever became significant problem nothing stops the coin from adopting another algorithm.
For PoW blocks people would simply choose the one that is more profitable to mine, completely disregarding the other one.