I'm not talking about mids and treble, but in terms of bass response, I'd love to hear Denon AH-C700 dynamic driver implemented in a CIEM of some description. I just love the bass response of that particular driver (far better than MG6 Pro driver, IMHO, though I know some people will spit their dummy out in response to this).
The AH-C700 dynamic driver has a beautifully crisp, deep, controlled, and natural way of portraying percussion. I don't know how it compares to the Merlin bass driver, as I haven't heard the Merlin (I've only heard/owned the Miracle, which, of course, is entirely BA).