Pariah is already finished afaik, and is due out in November this year. It will probably be available digitally in October. That is just 6 months away!
I think you might be in for a pleasant surprise then.
**Spoilers, don't read any more if you haven't read the Ravenor triology or short stories**
The retinues is where I would expect most of the action and drama to be focused on.
Fischig might be dead, but Nayl isn't, and will almost certainly make a return, along with Bequin and Medea.
I would expect there to be some very interesting moral dilemmas when the loyalties of the likes of Nayl and Kara are split between the old and current masters.
Just a few stabs in the dark as to some of the things I would consider doing if I was writing it.
In terms of kicking it all off, well, I actually see Kara as the key.
At the end of the last Ravenor book, she was in some pretty deep doodoo for concealing the fact that Thonius was possessed by the Daemon from Ravenor. Somehow, I don't see the =I= taking a sympathetic view of aiding and abetting a daemon.
There is no way Kara would not burn for what she did, but she is too great a character to kill off so lightly. But if in swoops Eisenhorn and rescues her from being executed by the =I=, well, that saves Kara and also gives Ravenor a reason to go after Eisenhorn.
On a similar theme, Ravenor himself is in some hot water over disobeying orders and all the mess he caused when going rogue to hunt Molotch. If Kara wasn't important enough or close enough for Eisenhorn to risk crossing the =I= to save, Ravenor would be. Especially if Eisenhorn needs Ravenor's help to avert some disaster or defeat some evil.
Afterwards, Ravenor hands himself in to the =I=, and is offered the chance to redeem himself and his band, if he hunts down Eisenhorn.
In terms of divided loyalties between the retinue members, I can actually see Patience being a prime candidate to be turned if Eisenhorn were to say, locate or even rescue her long lost sisters.
Remember, Ravenor lied to her when he first encountered and recruited Patience, he told her they were dead, when they were just taken and almost impossible to track down. If she ever found out the truth, it would fundamentally shake her trust and loyalty to Ravenor. If given the chance of being reunited with her sisters, I can easily see her being willing to turn on Ravenor in exchange.
In Salvation's Reach, it was mentioned the Ravenor 'died badly', being betrayed and murdered by a trusted aid would certainly fit that bill.