So you want that window rendered to 16-bit and have it as a mid-ground BGO? I can make it, I'll post it here when I'm done.
Edit:
Okay, it's done! I've made it replace the Blue SMW Door, that way it automatically goes in front of any BGO, but doesn't act like a foreground BGO, where the player will go behind it. I hope t's what you were after: http://www.mediafire.com/download/nngaa ... hy_Rex.zip