Haven't put any on the table yet, but have been thinking about it.
Caster-wise I guess options are Skarre 3, Denny 3, Denny 1. I don't include Skarre 2, because she hinges too much on Black Spot and likes combined arms better. Skarre 3 would be a jack gunline with 3-4 Leviathans, Denny 1 would be troops with as many Scharde Pirates and Ogrun as you can fit, perhaps some Marauders. Denny 3 would choose between the two or even be a mix of the 2.
In my opinion, the only reason for a jack gunline to exist in Slaughterfleet instead of Black Industries would be Dirge Seers, seeing as its our only access to Guidance. This is of course a very good reason, but be sure to include some if you make a list like this.
For a gun line, those would be my casters of choice as well.
Skarre 3 with her own powerful guns, guided fire and deceleration to protect your stuff at range can really tune up a ranged list.
Denny 3 pretty much relies on knocking down your opponent and efficiency of turning souls into focus for your jacks (leviathans and/or a kraken) to really take advantage of the pop and drop.
Denny 1 just debuffs your opponent with potentially -4 defense and/or -5 armor and really makes weaker guns hit really hard. With her, like Gamingdevil said, the more guns you have, the more mileage you get out of her debuffs, so troops really are the way to go with her.
Another caster I would consider is Mortenabra. With her interface rule and Deryliss's tune up rule, you can take a kraken or a sepulcher and turn them up to an 11 with the sheer volume of focus and free boosting you get from their abilities. Rerolls help too.
But the first three casters are strictly better with gun lines. Mortenabra is better with a 1-2 ranged jacks and some fast assassination support jacks like scavengers, stalkers, etc.