Spawning CTRL's and MACH's and linking them? That sounds awesome. *sigh* we could only wish though. I doubt Bungie would do that for us....lights sounds very likely, especially seeing the massive emphasis they put on the lighting in the update.
Forgeable lights = PWN! Openable/closable doors in forge = PWN! I have been hoping for the ability to make an almost completely dark map since I first tried forging. It would also go well with the doors because you could open them to let in light and close them to keep it out.