Hey! I have a new suggestion for MI:CE. Its rendering an object over another. An example is Links hair and eyes from Wind Waker,
Notice how his eyes and eyebrows 'overlap' his hair, while being under it. (I suck at explaining >.<)
Its probably a hard thing to do, (but I don't do 3D things in game maker... lol) but I think it'll be a nice addition for rigging things,
edit: Basically anime eyes and hair.