Good advice, great article. Although you should have probably said that it isn't a good idea to jump right into creating your own major mod until after you have worked on another project. Working on another project prior to leading a modding team should prove to be a valuable learning experience and would certainly make the development of your own mod move much smoother.
I agree, a good article, concise and really lets people know the basics.
Now, the only thing, it sounds like you were aiming it at small mods, ie the cs clones and the ones that are making mp only games excluding the very ambitious mmorpg mods. When it comes to sp, there are some differences to the formula.
For one, you may need some more people to work on it, as youre providing more actual content to the player vs mp that most of the content is in just playing with other people.
Another fact, writing a full design document before starting is great, but sometimes ill practice if its just one person, honestly I think a team of people, 2-4 people should be included into the design document, to really flesh out ideas and get a better overall flow of ideas. Instead of the "I think its fun sounding, so thats how its going to be!" mentallity. Really, thats up to whoever is making the mod, I just really think that other peoples input is vital in a games developement.
Now, for sp mods, like mine perse, we need to have closed testing, because we really dont want to release all of the story before the finished product, it would really diminish the overall game. Running a testing team is a task on its own, and really deserves its own article, but anyways Im rambling.
Overall a great article, maybe add in some things about sp mod specific topics, and well yeah,