TechWizzard, the build size of my install media is under 3.6GB. In your proofreading revision of my original draft you added the statement that the final ISO build would be approximately 4.6GB. Is that a typo on your part or is that difference due to the fact that you were using Ultimate for the build and I was using Professional?
I had additional updates installed at that point for Enterprise. I created a Professional version last night while beginning to write my version of the guide and the installer is 4.05GB. It contains the April Service Stacking Update, SP2/Convenience, May, July, August, and September Roll Ups.
TW, I also was not sure of there being 500+ updates to Windows 7 released since SP1. I don't seem to turn up that many, even when I take all the optional ones and drivers. Seems to be more like 200 for me when I check for them. But again, some of this difference may be explained by the fact that you are working from Ultimate and me from Professional. Anyway, I reworded that part to say just "hundreds."
Since SP1
might be ~300+ Updates. I'd lean more towards 400.
If you don't have SP1 and try to install from scratch (Windows 7 from 2012), you have an additional 150+ updates you need as prerequisites before you install SP1. After you install SP1, if the updater works it'll pull another 120 or so. After that you'll find a large batch of 230+, give or take a few. Then there is about 70 additional updates followed by 2-3 waves of 10-20 updates, finally followed by smaller batches in the single digits.
So to break it down... 150 + SP1 + 120 + 230 + 70 + ~50 + ~20 = ~600+ SO even if I am wildly off on one of those figures in there 500+ isn't unrealistic.
I will try to post a new draft with corrections later today.
I'm working on mine as well. I just need to go through the actual process of executing the commands step by step (the quick part). I've included adding SP1 manually within the instructions that users can skip over if they already have it and I plan on including a section at the end that explains how to integrate USB 3.0 drivers into your boot.wim so you can utilize USB 3.0 for faster installs.
I created an Introduction for those interested in actually learning DISM and to understand the process we have been going over the last few weeks here. Obviously this can be skipped or posted separate from the actual instructions. When I got into "How to do it" I just got straight to the point to avoid having two guides that are too identical. I don't explain how to mount images or ask them to name things specifically - I only offer examples for the sake of assuming people will understand they are creating folders to manipulate files.