I like the idea of an internal switch based on the handle though. Possible a slim reed switch and a very small magnet would do the trick.

I looked, and on my player at least, there's a spot on either side where the handle hinge assemblies reach the bottom of their travel. It's right next to the motherboard mounting screws. Seems like something clever with a reed switch attached to one of those screws would do it.

I just worry about reed switches... I had an old Sony car CD player that depended on reed switches to know how to mechanically load the CD into the player, and they were always failing and needing to be replaced.