If I'm not mistaken, I think Coin-coin wants to be able to queue up -- or run simultaneously -- multiple camera shakes, rather than shake individual layers. MagiCam can't handle that itself, but one could always setup a queue that initiates camera shakes in sequence.
Yeah, I just created a function to do that. It seems to work fine with multiple camera shakes, even on scenes with a lot of parallax.
Which reminds me: The zoom limits sometimes get a little shaky when the camera is near the outer zoom limits. Not really related to camera shake, just something I noticed while playtesting.