No. I work as a terminal superintendent for a stevedoring company.
Port security is pretty insane in this post 9-11 world.
If container ships came in and tied up to my dock, and were armed as you suggest, we would have even more security / operational "issues". I don't even want to think about what we would have to do, or what it would cost us as a terminal operator.
Maybe if there was US Coast Guard cooperation and the arms could be removed before the vessel arrives dockside, it would be okay, but I don't want armed containerships coming into port. (Neither does the Coast Guard)
I also see problems with the fact that pretty much all cargo and container ships operate under a foreign flag. So what you are suggesting would involve, for example, Chinese owned and operated vessels coming into US waters and tying up to US docks, with 50 mils and RPG's ready to fire. There is no way that could happen.