There's really no comparison between focused discussion groups and the community manual. It's really unfair to the CM to even make such a comparison.
Mentoring, and the free expression of ideas is what draws me to the forums. I'm not really interested in re-reviewing the CM on a day-to-day basis; I much prefer the open discussion. I mean it's the difference between a teacher and a textbook. No one would suggest that teachers aren't necessary in the classroom because all the answers are already in the book. I think the CM serves it's role well as a decent primer.
There's already a breakout for modding efforts... So I guess what you're after are subtopics under the general SH3 category. I'm not necessarily against the idea.
What categories would you propose? I think the most challenging part of doing something like that would be the natural overlap between proposed categories. As well as the fact that you'd almost have to consolidate the SH3 & SH4 forums so that topics on navigation and attack plotting theory for instance wouldn't exist in both.
I guess the flip-side to the argument would be that if there were too many categories, noobs would become overwhelmed and have no idea which forum is appropriate for their questions... Totally aside from the fact that forum admins workload would have to increase in the sense that folks would post off-topic and the admins would have to educate new posters and/or spend time moving things around.
I've seen on other forums where they've instituted a system for helping to classify the post by using a mandatory dropdown selection next to the title (a set list of keywords) to help assist in refining search results.