It sounds like what you're asking for is a way to force Windows Update to run, instead of waiting for the scheduled task to do it. I Google searched for "command line Windows Update" and that gave me links which say to use "wuauclt /detectnow /updatenow" without quotes. I haven't tested it, but if that works (try it on a live desktop first) it'll need to be put into NTLite's post-setup section for User (After logon), and once you reach the desktop after installing the operating system it should start Windows Update automatically.
