I know zilch about Warhammer, and this is essentially a brainstorming, but here goes:
The king information that one of the old and powerful noble houses is staging a coup against him. One house is lead by a cunning merchant (and leader of the biggest thieves guild around). There are rumors that one house has very good connections to the TG, but no one knows who it is precisely. Nevertheless, the king suggests taking care of them. What he doesn't know is that they're (this once) innocent. What the players don't know is that the thieves are blackmailing the king with whatever info (anonymously of course), and the king wouldn't mind seeing the thieves taken care of either way. Regardless, the thieves don't care about (in fact, discourage) any putsches, because they have the king on a leash that is as short as it can get.
On the other side is, for example, the house that has been supplying the kingdom with hierophants for generations and are above suspicion. They have captured (read: hired) the "heretic" who leaks the putsch info, blaming a third house (dunno, a house of accomplished wizards?). The heretic would later be given over to the temple to be executed (or let go, so maybe the players could spot him later in the city or something) by inquisitors. Their aim, I dunno.. create enough mayhem to collapse the corrupt infrastructure and cleanse the nobility, or simply to weaken the power bases to allow a neighboring country to invade and the priests would gain greater worldly benefits and/or more followers (other country would sanction this faith or something) as compensation. Most of the local church don't know his of course, but they don't need to..