Then adding the corresponding dock connector on a sled would be trivial.

I wouldn't call cutting a huge hole in the back of the player casing "trivial". That's some pretty thick stainless steel. Especially considering that it's an EOL unit and not easily replaced.

Since docked ethernet is so easy to do with the existing sled and ports, why not just do it that way? I'm telling you, setting up docked ethernet with Jim Hogan's method was absolute child's play, it works reliably (at least on mine), and doesn't require cutting a hole in the player. It doesn't even require modding the sled, I screwed the piece of wood to the hole in the back of the sled so it can be removed and returned to factory spec in seconds.