@ The Librarian
Good reminder about that enigmatic "transtater" technology mentioned in "A Piece of the Action" (Captain Kirk couldn't drive a combustion vehicle!). Though I do not believe it used tiny dilithium diamonds (there was no hint that the Iotians might have such resources), the closing remarks in this episode suggested that the imitation of this technology could enable the Iotian to overtake the Federation. Which inevitably would assign dilithium crystals a less important role in the "big" picture.
Come to think about it, we discuss properties of an exotic substance we do not really have a clue how it actually would work IRL. Whether it amplifies energy or stores large amount of energies or has the capability of doing both things is not the (warp) core issue as long as we agree that the energy coming from these crystals either way is essential to have warp drive capability.