The big advantage you have over pirates is with naval weapons, which most pirate hunters and merchants won't be able to acquire. The reality is that most pirates have probably faced small arms fire many times more than the crew of a "weapons mother ship." They will be a lot less afraid of our M240s than we will be of their RPKs or whatever else they're fielding, having spent their lives in constant warfare.
/parade
Now, something on the order of a 25mm or larger is going to ruin a pirate's day....that's why navies are needed to do the job.
You know, I'm thinking out loud here, so bear with me.
Why can't a private corporation buy, say around a 200-300 foot ship as a mother ship, and operate a handful of 80 foot PT-type boats. Go the route of the PT gunboats, strip them of the torpedo fittings and equip them with 40mm cannons and several twin .50 mounts. Considering the Bofors 40mm gun has a range of somewhere around 3 miles, I think we can safely bet that we could engage them *long* before they could engage us with small arms and RPG's. The M2's have an effective range of 2000 meters, 10 TIMES the effective range of an RPG7, and double the MAXIMUM range at which an RPG self detonates. Additionally, the AK47 has an effective range of 400 meters... Again, the M2 can engage at 5 TIMES that distance.
Frankly, I don't see why navies are needed... Set up your mother ships at either end of the run, and your PT gunboats can escort vessels back and forth. Set up a fee schedule based on # of escort boats you want and tonnage of your vessel... And then it's just a matter of motoring a couple hundred yards away from the escortee....