I am not opposed in principle to a forum sub-board, which has been suggested before (but my responses were never really followed up), but I don't really see a clear and easily understood distinction of topic types for it and the main board:
A board for servers doesn't make much sense, because more things are dependant on the server being played on than most other mods, meaning almost all of the current threads are related to servers in some way; a separate board for each server would be unsustainable and contrary to the decentralized design of the mod.
I don't think a board just for "in character" posts makes very much sense either, because very little of the current posting is typed out from that perspective, and it mostly belongs in the game, rather than the forums. Calling it a board for factions or organisations seems more distinctive, but I would be wary of of stickying that sort of thread or having people moderate them more restrictively than the current main board, to avoid dragging the overall mod down with personality conflicts and elitist traditionalism (as I have experienced in other projects, not related to M&B). The mod is designed to be a dynamic world that changes according to people playing the game, not a static environment tightly controlled by people posting on the forums or other communication methods, with major occurrences preplanned a long time before then acted out by administrator force; there are plenty of other projects out there with that style, and I have no interest in making yet another one - people can choose to host servers working that way, but the overall mod will not be bound to them.
If people can bring forward specific suggestions that would keep a possible additional mod board fairly neutral, judged by simple, understandable rules and distinctions, we can discuss this further.