Q u o t e: Why does the other systems promote grinding? Because everyone will probably want a sound amount of keys of all types before a playing session so they do not have to leave unopened chests behind. And if you happen to not have a specific key, that is exactly what you will have to do without any choice, imo, bad design.
I think my suggestion eliminates the grind factor. If the key was the first item to appear, and said key triggered a quest that would lead to the game generating a matching chest, then there is no grindfest and the participation in the quest is still entirely voluntary. It wouldn't require carrying around a keyring full of variously colored/sized keys (unless the player chose to save the key quest for a later time) and it wouldn't force the player to backtrack to find the chest or its key.
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