I scoured the net for info on the campaign systems used in Mighty Empires, and found this PDF. It is a campaign system for warhammer, but an older version (second or third ed. I think?). I flipped through it and I think there are many things in there that any dungeon master or campaign maker for Mordheim can draw inspiration from.
Take a look, it is pretty cool stuff (especially the old art and drawings have a very special feel about them