Chris,
We're running a six player campaign as well. Three Saxon and three Romano British players.
Each RB player controls two provinces in North England. Of course once he loses both it's game over for him.
So far one of the Saxons made Warlord but lost heavily in his first battle. Out for 9 months. The other Saxon is now ready for a land grab and the thrird still needs to do a succesful raid.
One of the RB players has already upgraded a Levy unit to warrior and added a unit of skirmishers to his army. he also has a priest helping him out.
The other RB player has a priest as well and two additional warriors in one unit.
I've chosen North England,Rheged, Coriosoptimum, Caer Brogwm and so in anticipation of the Raiders supplement. Then the Irish, Scotti and Picts will also be able to raid these provinces and it will become quite hectic.
We are using the additions concerning industry and fortifications as suggested in the 2012 TFL Summer Special.
Have fun!