One more thing, these are the amount of threads that I believe this would require:

Story Thread: Quite self-explaining. Not actually necessary, but adds some flavour and is good for developing characters. This thread could also be used for correspondance between characters (only adressed characters can "read" the letters, so this would also make this the thread for plotting).

Diet/Parliament: Solely for political discussions.

OOC: Again, quite self-explaining.

Battle Report Thread: As above...

And then finally a thread were we gather all the info on our empire and some kind of timeline.