My father was an armorer when he was in Europe during WWII. He worked on Quad-50’s and Bofors.
I could see Quad-50’s on such a boat with a few anti-tank weapons for good measure.
http://www.rt66.com/~korteng/SmallArms/PrincipalWeapons.htm
“Quad .50: A half-track mounting four .50s capable of being fired as a unit. Developed as an anti-aircraft weapon, as an antipersonnel weapon it was capable of hurling an immense amount of fire into hillsides and valleys against advancing infantry, or long-range harassing fire against enemy movement routes at night. Firing as many as 100,000 rounds a day, the Quad .50 could go over hills like a vacuum cleaner, sucking them devoid of life.”
The Germans had something similar, a `Werbel’ (Whirlwind’)? and used it a lot after they lost control of the air.
That’d work!
I was thinking of something the Marines used— 4 recoilless rifles? An Ontos(?) That might be even better for cartel caravan work.
Bofors twin mount like the AA mounts on WWII USN ships.